[Transcriber's Notes: The following change has been made to the text: Page 631, added closing parenthesis to "(genus Eutamias of California)"] The Baculum in the Chipmunks of Western North America BY JOHN A. WHITE University of Kansas Publications Museum of Natural History Volume 5, No. 35, pp. 611-631, 19 figures in text December 1, 1953 University of Kansas LAWRENCE 1953 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, A. Byron Leonard, and Robert W. Wilson Volume 5, No. 35, pp. 611-631, 19 figures in text December 1, 1953 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1953 [Illustration] 24-8968 The Baculum in the Chipmunks of Western North America By JOHN A. WHITE CONTENTS PAGE Introduction 613 Methods, Materials, and Acknowledgments 614 Variation 614 Key to the Bacula of the Species of Eutamias of Western North America 615 Accounts by Species 616 _Eutamias alpinus_ 616 _E. minimus_ 617 _E. townsendii_ 618 _E. sonomae_ 619 _E. amoenus_ 619 _E. dorsalis_ 620 _E. merriami_ 621 _E. quadrivittatus_ 621 _E. ruficaudus_ 622 _E. cinereicollis_ 624 _E. quadrimaculatus_ 624 _E. speciosus_ 625 _E. panamintinus_ 625 _E. umbrinus_ 626 _E. palmeri_ 627 _E. bulleri_ 627 Figures 1-19. Lateral views of bacula 629 Discussion 630 Literature Cited 631 INTRODUCTION The baculum is the bony part of the penis. In the species of the subgenus _Neotamias_ the proximal part of the baculum is termed the shaft, and the distal upturned part is termed the tip. On the dorsal side of the tip there is a longitudinal ridge termed the keel. The proximal end of the shaft is termed the base (see fig. 19). Depending on the species, the shaft varies from 2.11 to 5.28 mm. in length, and the base may or may not be widened or deepened. The purpose of this report is to: (1) Show the usefulness of the structure of the baculum as a taxonomic character in chipmunks; and (2) compare a classification based on the structure of the baculum with a classification based on the structure and appearance of the skull and skin. METHODS, MATERIALS, AND ACKNOWLEDGMENTS The bacula which were borrowed from the University of Michigan, Museum of Zoology, were processed according to the method described by Friley (1947:395-397), whereas all others were processed according to the method described by White (1951:125). Thus the bacula that were borrowed from the University of Michigan, are maintained there in a separate collection, whereas the bacula borrowed from other museums and those that are at the University of Kansas, Museum of Natural History, are housed with the skulls of the corresponding specimens. All measurements of the bacula were made by means of an eyepiece micrometer. A total of 194 bacula were seen. All of these are in the Museum of Natural History of the University of Kansas, unless otherwise indicated by the following symbols: BS United States Biological Surveys Collection. CN Chicago Natural History Museum. LA Los Angeles County Museum. MM University of Michigan, Museum of Zoology. NM United States National Museum. UU University of Utah, Museum of Zoology. I am grateful to Professor E. Raymond Hall for guidance in my study and thank Drs. Robert W. Wilson, Keith R. Kelson, and Edwin C. Galbraith, as well as other friends and associates of the Museum of Natural History, University of Kansas, for encouragement and valuable suggestions. Dr. William L. Jellison, United States Public Health Service, aided me in part of my field work and kindly sent me some specimens of chipmunks. My wife, Alice M. White, made the illustrations and helped me in many ways. For the loan of bacula I thank Dr. William H. Burt, University of Michigan, Museum of Zoology. For permission to search for bacula on study skins, and to process those that were found, I thank Miss Viola S. Schantz, United States Fish and Wildlife Service, Mr. Colin C. Sanborn, Chicago Natural History Museum, Mr. Kenneth E. Stager, Los Angeles County Museum, Dr. David H. Johnson, United States National Museum, and Dr. Stephen D. Durrant, Museum of Zoology, University of Utah. Assistance with field work is acknowledged from the Kansas University Endowment Association, the National Science Foundation and the United States Navy, Office of Naval Research, through contract No. NR 161 791. VARIATION _Individual variation._--Individual variation is small. This is shown by a coefficient of variability of only 3.85 in the length of the shaft in a series of 12 specimens of _E. umbrinus umbrinus_ from Paradise Park, 21 mi. W and 15 mi. N Vernal, 10,050 ft., Uintah County, Utah. _Variation with age._--In the chipmunks the baculum varies but little with age. In the youngest specimens that I have taken, the M3 and m3 have not yet erupted and there is no wear on P4 and p4; nevertheless, the baculum in these specimens has nearly an adult configuration and size. In juvenal _Eutamias minimus_ the tip of the baculum is longer in relation to the length of the shaft than it is in adults; the tip is 18 to 28 per cent of the length of the shaft in adults, as opposed to 29 to 32 per cent in juveniles. _Aberrations._--In a small percentage of specimens of _E. minimus_ and _E. umbrinus_ the baculum is small and S-shaped, even in adults. _Variations of taxonomic worth._--Variations in this category are described in the section immediately following the key. KEY TO THE BACULA IN EUTAMIAS OF WESTERN NORTH AMERICA 1. Distal 1/2 to 2/3 of shaft markedly compressed laterally; base markedly widened. 2. Distal 1/2 of shaft laterally compressed and curved downward to base of tip. 3. Height of keel 1/2 of length of tip; keel markedly enlarged. _Eutamias bulleri_, p. 627 3'. Height of keel 1/4 of length of tip; keel not markedly enlarged. _Eutamias umbrinus_ and _E. palmeri_, pp. 626, 627 2'. Distal 2/3 of shaft laterally compressed and curved downward to base of tip. 4. Base of keel 1/3 of length of tip; angle formed by tip and shaft less than 100° _Eutamias speciosus_, p. 625 4'. Base of keel 1/2 of length of tip; angle formed by tip and shaft more than 102° _Eutamias panamintinus_, p. 625 1'. Distal 1/12 to 2/5 of shaft slightly compressed laterally; base not markedly widened. 5. Shaft thin; shaft less than .20 mm. in diameter at widest point. 6. Ridges on either side of keel enlarged, partially obscuring lateral view of keel; height of keel 1/10 of length of tip. _Eutamias sonomae_, p. 619 6'. Ridges on either side of tip not enlarged, not partially obscuring lateral view of keel; height of keel at least 1/7 of length of tip. 7. Base not widened or dorsoventrally thickened. 8. Shaft more than 4.5 mm. in length; tip 16 per cent of length of shaft; shaft strongly incised on dorsal side of base _Eutamias merriami_, p. 621 8'. Shaft less than 4.4 mm. in length; tip more than 25 per cent of length of shaft; shaft not incised on dorsal side of base. 9. Height of keel 1/7 of length of tip; angle formed by tip and shaft distinct _Eutamias alpinus_, p. 616 9'. Height of keel at least 1/5 of length of tip; angle formed by tip and shaft poorly defined. 10. Height of keel 1/3 of length of tip; angle formed by tip and shaft 140° _Eutamias dorsalis_, p. 620 10'. Height of keel 1/5 of length of tip; angle formed by tip and shaft 130° or less. 11. Tip more than 29 per cent of length of shaft. _Eutamias amoenus_, p. 619 11'. Tip less than 28 per cent of length of shaft. _Eutamias minimus_, p. 617 7'. Base widened and dorsoventrally thickened. _Eutamias townsendii_, p. 618 5'. Shaft thick; shaft more than .25 mm. in diameter at widest point. 12. Length of shaft less than 3.00 mm.; length of tip less than 1.10 mm. _Eutamias quadrivittatus hopiensis_, p. 622 12'. Length of shaft more than 3.10 mm.; length of tip more than 1.15 mm. 13. Tip less than 28 per cent of length of shaft. _Eutamias quadrimaculatus_, p. 624 13'. Tip more than 29 per cent of length of shaft. 14. Angle formed by tip and shaft more than 140°; ridges on either side of tip indistinct. _Eutamias cinereicollis_, p. 624 14'. Angle formed by tip and shaft less than 135°; ridges on either side of tip distinct. 15. Shaft less than 3.65 mm. in length, and .55 mm. or less in diameter at widest point. _Eutamias quadrivittatus quadrivittatus_, p. 621 15'. Shaft usually more than 3.65 mm. in length, but when shorter, diameter is .60 mm. or more at widest point. 16. Diameter of shaft at widest point less than .58 mm.; tip less than 35 per cent of length of shaft. _Eutamias ruficaudus ruficaudus_, p. 622 16'. Diameter of shaft at widest point more than .65 mm.; tip more than 40 per cent of length of shaft. _Eutamias ruficaudus simulans_, p. 623 ACCOUNTS BY SPECIES #Eutamias alpinus# (Merriam) Figure 1 Pelage silky; tail bright orange beneath; markings relatively obscure; size small; skull broad, flattened, and large in proportion to body. Baculum: Shaft thin; keel low, 1/7 of length of tip; tip 39 per cent of length of shaft; angle formed by tip and shaft 135°; distal 1/3 of shaft slightly compressed laterally; base slightly wider than shaft; shaft short, 2.17 mm. Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base not markedly widened, and shaft thinner; from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_, and _E. quadrimaculatus_, in shaft thinner, baculum shorter; from _E. townsendii_, in base not dorsoventrally thickened, base not so widened; from _E. sonomae_, in ridges on either side of tip not enlarged, base not dorsoventrally thickened; from _E. amoenus_, _E. minimus_, and _E. dorsalis_, in keel lower, angle formed by tip and shaft more distinct; from _E. merriami_, in baculum markedly shorter, base not incised dorsally. _Specimen examined_: One from Big Cottonwood Meadows, S of Mount Whitney, 10,000 ft., Inyo Co., California (CN). #Eutamias minimus# (Bachman) Figure 2 Coloration varying from light to dark depending on subspecies; size small to medium; rostrum short and stout. Baculum: Shaft thin; keel low, 1/5 of length of tip; tip 18 to 28 per cent of length of shaft; angle formed by tip and shaft 125°; distal 1/2 of shaft slightly compressed laterally; shaft short to long, 2.44 to 4.35 mm. Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in shaft thinner, base not markedly widened; from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_, and _E. quadrimaculatus_, in shaft thinner, tip shorter; from _E. amoenus_, in tip less than 28 per cent of length of shaft; from _E. dorsalis_, in angle formed by tip and shaft smaller; from _E. townsendii_, in tip less than 28 per cent of length of shaft, angle formed by tip and shaft 125° instead of 130°; from _E. sonomae_, in ridges on either side of tip less well-developed, keel higher; from _E. merriami_, in shaft shorter (less than 4.40 mm.), base not incised, tip proportionally longer. For comparison with _E. alpinus_ see the account of that species. In most places where _E. minimus_ and _E. amoenus_ occur together they can be distinguished without recourse to the baculum, but at Banff and Canmore in western Alberta, recourse to the baculum is almost necessary. There, as elsewhere, they can be distinguished readily by the shape of the bacula. _Specimens examined_: 72. _Eutamias minimus borealis_: Alberta: Canmore, 1 (BS). _E. m. cacodemus_: South Dakota: _Shannon Co._: Quinn's Draw, Cheyenne River, 1 (NM); 14 mi. N and 5 mi. W Rockyford, 3,200 ft., 1. _E. m. confinis_: Wyoming: _Big Horn Co._: 17 mi. E and 3 mi. S Shell, 9,000 ft., 1; 9 mi. E and 9 mi. N Tensleep, 8,200 ft., 1. _Washakie Co._: 9 mi. E and 4 mi. N Tensleep, 7,000 ft., 1. _E. m. consobrinus_: Montana: _Madison Co._: 26 mi. NW West Yellowstone, 6,100 ft., 1. Wyoming: _Sublette Co._: 5 mi. E and 9 mi. N Pinedale, 9,100 ft., 2. _Uinta Co._: 10 mi. S and 1 mi. W Robertson, 8,700 ft., 1; 13 mi. S and 2 mi. E Robertson, 9,200 ft., 2. Utah: _Uintah Co._: Paradise Park, 21 mi. W and 15 mi. N Vernal, 10,050 ft., 8. Colorado: _Jackson Co._: 9-1/2 mi. W and 2 mi. N Walden, 8,400 ft., 1. _E. m. jacksoni_: Michigan: _Menominee Co._: 7 mi. E Stephenson, 4 (MM). Wisconsin: _Juneau Co._: Camp Douglas, 1 (NM). _E. m. minimus_: Wyoming: _Natrona Co._: 27 mi. N and 1 mi. E Powder River, 6,075 ft., 1; 16 mi. S and 11 mi. W Waltman, 6,950 ft., 1; Sun Ranch, 5 mi. W Independence Rock, 6,000 ft., 1. _Uinta Co._: 8-1/2 mi. W Ft. Bridger, 7,100 ft., 1; 2 mi. W Ft. Bridger, 6,700 ft., 1; unspecified, 3 (MM). _Sweetwater Co._: Kinney Ranch, 21 mi. S Bitter Creek, 6,800 ft., 1; 32 mi. S and 22 mi. E Rock Springs, 7,025 ft., 3; 33 mi. S Bitter Creek, 1. _E. m. operarius_: Wyoming: _Converse Co._: 21-1/2 mi. S and 24-1/2 mi. W Douglas, 1. _Carbon Co._: 8 mi. N and 19-1/2 mi. E Savery, 8,800 ft., 1; 5 mi. N and 5 mi. E Savery, 6,900 ft., 1. _Albany Co._: 3 mi. ESE Browns Peak, 10,000 ft., 1. Colorado: _Rocky Mountain National Park_, 1 (MM). _Boulder Co._: Unspecified, 1 (NM). _Gunnison Co._: 7 mi. S and 7 mi. W Gunnison, 8,150 ft., 1. _Saguache Co._: 5 mi. N and 22 mi. W Saguache, 10,000 ft., 2. _Archuleta Co._: Unspecified, 1 (MM); 5 mi. S and 25 mi. W Antonito, 9,600 ft., 3. _Costilla Co._: Unspecified, 1 (MM). New Mexico: _Taos Co._: 23 mi. S and 6 mi. E Taos, 8,750 ft., 3. _E. m. pallidus_: Montana: _Fergus Co._: Unspecified, 1 (MM). _Sweetgrass Co._: Unspecified, 1 (MM). Wyoming: _Campbell Co._: 4 mi. S and 3 mi. W Rockypoint, 1; Ivy Creek, 8 mi. W and 5 mi. N Spotted Horse, 3; Middle Butte, 6,010 ft., 38 mi. S and 19 mi. W Gillette, 1. _E. m. silvaticus_: South Dakota: _Pennington Co._: Unspecified, 1 (MM). _Custer Co._: Unspecified, 2 (MM). Wyoming: _Weston Co._: 1-1/2 mi. E Buckhorn, 6,150 ft., 3. #Eutamias townsendii# (Bachman) Figure 3 Pelage tawny to olivaceous; stripes obscure and underparts tawny, or stripes conspicuous and underparts white; tail slender and sparsely haired; size large; skull largest in the subgenus _Neotamias_. Baculum: Shaft thin; keel low, 1/5 of length of tip; tip 32 per cent of length of shaft; angle formed by tip and shaft 130°; distal 1/5 of shaft slightly compressed laterally; base deeper and wider than shaft; shaft short, 2.24 mm. Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base not markedly widened, shaft thinner, tip proportionally shorter; from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_, and _E. quadrimaculatus_, in shaft thinner, baculum shorter and smaller; from _E. sonomae_, in ridges on either side of tip not enlarged, keel proportionally higher; from _E. amoenus_ and _E. dorsalis_, in base widened and thickened, baculum usually shorter; from _E. merriami_, in being markedly shorter, and having base widened and deepened but not incised dorsally. For comparisons with _E. alpinus_ and _E. minimus_ see the accounts of those species. _Specimens examined_: 2. _E. townsendii townsendii_: Oregon: _Multnomah Co._: Portland, 1 (NM). _E. t. cooperi_: Oregon: _Hood Co._: Brooks Meadow, 4,300 ft., 9 mi. ENE Mount Hood, 1. #Eutamias sonomae# Grinnell Figure 4 Upper parts rich reddish, more or less dulled by gray; backs of pinnae of ears nearly bare; tail long and bushy; size large; skull large, long, and narrow; rostrum deep. Baculum: Shaft thin; keel low, 1/10 of length of tip; tip 27 to 31 per cent of length of shaft; angle formed by tip and shaft 130°; distal 1/4 of shaft slightly compressed laterally; base deeper and wider than shaft; shaft of medium length, 3.03 to 3.30 mm.; ridges on either side of tip strongly developed, partly obscuring keel from side. Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in ridges on either side of tip strongly developed, shaft thin, base not markedly widened, tip proportionally shorter; from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_, and _E. quadrimaculatus_, in shaft thin, ridges on either side of tip strongly developed, baculum shorter; from _E. amoenus_ and _E. dorsalis_, in keel lower, ridges on either side of tip strongly developed, base thicker and wider; from _E. merriami_, in markedly shorter, ridges on either side of tip strongly developed, tip proportionally longer, base wider and deeper but not incised dorsally. For comparisons with _E. alpinus_, _E. minimus_, and _E. townsendii_, see the accounts of those species. _Specimens examined_: 5. _E. sonomae alleni_: California: _Marin Co._: Unspecified, 1 (NM). _E. sonomae sonomae_: California: _Siskiyou Co._: Salmon Mts., W slope, W of Etna, 1 (BS). _Shasta Co._: Redding, 1 (BS). _Mendocino Co._: Cahto, 1 (BS). #Eutamias amoenus# (J. A. Allen) Figure 5 Upper parts generally ochraceous; venter frequently buffy; size small to medium; zygomatic arches usually appressed to cranium; frequently difficult to distinguish from _E. minimus_. Baculum: Shaft thin; keel low, 1/5 of length of tip; tip 30 to 35 per cent of length of shaft; angle formed by tip and shaft 130°; distal 1/5 of shaft slightly compressed laterally; shaft short, 2.37 to 2.96 mm. Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base not markedly widened, shaft thinner; from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_ and _E. quadrimaculatus_, in shaft thinner, baculum usually shorter, tip shorter; from _E. dorsalis_, in keel lower, angle formed by tip and shaft 130°, usually smaller; from _E. merriami_, in being markedly shorter, and in base not being dorsally incised, tip proportionally longer. For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, and _E. sonomae_, see the accounts of those species. Bacula from skins labeled as _E. amoenus amoenus_ from, Lardo, Valley Co., Idaho (MM), Butte Co., Idaho (MM), and Boise National Forest, Idaho (BS), resemble the bacula of _E. umbrinus_, and critical study of other features of these specimens probably will show that they are _E. umbrinus_. _Specimens examined_: 23. _E. amoenus amoenus_: Oregon: _Klamath Co._: Fort Klamath, 1 (MM). Idaho: _Valley Co._: Lardo, 1 (BS). _Butte Co._: Unspecified, 1 (MM). Boise National Forest, 1 (BS). _E. a. ludibundus_: British Columbia: Moose Lake, 1 (NM). _E. a. luteiventris_: Alberta: Banff, 2 (BS). Montana: _Flathead Co._: 1 mi. W and 2 mi. S Summit, 5,000 ft., 1. _Teton Co._: 17-1/8 mi. W and 6-1/2 mi. N Augusta, 5,100 ft., 2. _Missoula Co._: Unspecified, 1 (MM). Idaho: _Idaho Co._: 20 mi. S and 2 mi. E Grangeville, 2. _Fremont Co._: 7 mi. W West Yellowstone, 7,000 ft., 5; 9 mi. SW West Yellowstone, 8,500 ft., 1. Wyoming: _Teton Co._: 2-1/2 mi. N and 3-1/2 mi. E Moran, 7,225 ft., 1. _E. a. monoensis_: California: _Mono Co._: Leevining Creek, 1 (NM). _E. a. vallicola_: Montana: _Ravalli Co._: Bass Creek, 3-1/2 mi. NW Stevensville, 3,750 ft., 2. #Eutamias dorsalis# (Baird) Figure 6 General tone of upper parts smoky gray; dorsal stripes indistinct or obsolete; skull large. Baculum: Shaft thin; keel low, 1/5 of length of tip; tip 29 to 40 per cent of length of shaft; angle formed by tip and shaft 140°; distal 1/2 of shaft slightly compressed laterally; shaft short to medium, 2.64 to 3.69 mm. Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base not widened, shaft thinner; from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_, and _E. quadrimaculatus_, in shaft thinner, baculum usually shorter; from _E. merriami_, in shaft markedly shorter, base not incised dorsally, tip proportionally longer. For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E. sonomae_, and _E. amoenus_, see the accounts of those species. _Specimens examined_: 12. _E. dorsalis dorsalis_: Arizona: _Yavapai Co._: 3 mi. N Ft. Whipple, 5,000 ft., 1 (BS). _Gila Co._: Carr's Ranch, Sierra Ancha Mountains, 1 (BS). _Pima Co._: Unspecified, 1 (MM). New Mexico: _Valencia Co._: Mount Taylor, 1 (MM); 1 mi. N Cebolleta, 1 (MM). _Socorro Co._: San Mateo Mountains, 1 (BS). _Chihuahua_: Sierra Madre, near Guadalupe y Calvo, 3 (BS). _E. d. utahensis_: Wyoming: _Sweetwater Co._: W side Green River, 1 mi. N Utah Border, 1. Colorado: _Moffat Co._: Escalante Hills, 20 mi. SE Ladore, 1 (BS). Arizona: _Coconino Co._: Ryan, 1 (BS). #Eutamias merriami# (J. A. Allen) Figure 7 General tone of upper parts grayish; cheeks and underparts white, more or less dulled by gray; size large; skull large. Baculum: Shaft thin; keel low, 2/5 of length of tip; tip 16 per cent of length of shaft; angle formed by tip and shaft 130°; distal 1/10 of shaft slightly compressed laterally; base incised dorsally; shaft markedly long, 4.88 mm. Differs from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base incised dorsally, base not widened, shaft thinner, tip proportionally shorter; from _E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_, and _E. quadrimaculatus_, in base incised dorsally, shaft thinner, tip proportionally much shorter. For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E. sonomae_, _E. amoenus_, and _E. dorsalis_, see the accounts of those species. _Specimens examined_: One from Mount Piños, Ventura Co., California (LA). #Eutamias quadrivittatus# (Say) Figures 8-10 Color bright and tawny; size medium to large; braincase widened. Baculum of _E. q. quadrivittatus_: Shaft thick; keel proportionally low, 1/4 of length of tip; tip 30 to 44 per cent of length of shaft; angle formed by tip and shaft 130°; distal 1/3 of shaft slightly compressed laterally; shaft long, 3.17 to 3.62 mm. Differs from _E. q. hopiensis_, in baculum larger, angle formed by tip and shaft less distinct; from _E. ruficaudus ruficaudus_, in shaft and tip proportionally shorter; from _E. r. simulans_, in keel proportionally lower, shaft usually shorter and narrower; from _E. cinereicollis_, in shaft shorter, angle formed by tip and shaft larger, ridges on either side of tip more distinct; from _E. quadrimaculatus_, in tip proportionally shorter, shaft shorter; from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base not markedly widened, shaft longer, angle formed by tip and shaft larger. For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E. sonomae_, _E. amoenus_, _E. dorsalis_, and _E. merriami_, see the accounts of those species. Baculum of _E. q. hopiensis_: Shaft thick; keel proportionally low, 1/3 of length of tip; tip 34 per cent of length of shaft; angle formed by tip and shaft 130°; distal 1/3 of shaft slightly compressed laterally; shaft short, 2.64 mm. in length. Differs from _E. ruficaudus ruficaudus_, _E. r. simulans_, _E. cinereicollis_, and _E. quadrimaculatus_, in being shorter, proportions as in _E. q. quadrivittatus_; from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base not markedly widened, angle formed by tip and shaft larger; from _E. alpinus_, _E. minimus_, _E. townsendii_, _E. sonomae_, _E. amoenus_, _E. dorsalis_, and _E. merriami_, except for smaller size, as in _E. q. quadrivittatus_. Bacula of _E. q. hopiensis_ from northeastern Arizona are like those in typical _E. q. quadrivittatus_. The specimens from this region, to judge from parts of the animal other than the baculum, are intergrades between _E. q. hopiensis_ and _E. q. quadrivittatus_. Specimens from near Moab, Grand Co., Utah, are typical _E. q. hopiensis_ and the bacula of these specimens are considerably smaller than those of specimens of typical _E. q. quadrivittatus_. No bacula are known to me that are structurally intermediate between those of _E. q. quadrivittatus_ and _E. q. hopiensis_. _Specimens examined_: 21. _E. quadrivittatus quadrivittatus_: Colorado: _Gunnison Co._: Sapinero, 1 (BS). _Chaffee Co._: Unspecified, 1 (MM). _Saguache Co._: 5 mi. N and 22 mi. W Saguache, 10,000 ft., 1. _Fremont Co._: Canon City, 3 (BS). New Mexico: _Rio Arriba Co._: Dulce, 1 (BS). _Taos Co._: 23 mi. S and 6 mi. E Taos, 8,750 ft., 4. _Union Co._: Sierra Grande, 1 (BS). _Valencia Co._: Mirror Spring, Mt. Taylor, 3 (MM). _Torrance Co._: S end, E slope, Manzano Mountains, 2 (BS). _E. quadrivittatus hopiensis_: Utah: _Grand Co._: Mouth of Nigger Bill Canyon, E side Colorado River, 4 mi. N Moab Bridge, 4,500 ft., 1 (UU); Moab, 4,500 ft., 1 (UU). Arizona: _Apache Co._: Tunicha Mountains, 1 (BS). #Eutamias ruficaudus# Howell Figures 11-12 General tone of upper parts dark tawny; size medium; braincase narrowed. Baculum of _E. r. ruficaudus_: Shaft thick; keel proportionally low, 1/4 of length of tip; tip 31 to 33 per cent of length of shaft; angle formed by tip and shaft 120°; distal 2/5 of shaft slightly compressed laterally; base slightly widened; shaft long, 4.09 to 4.56 mm. Differs from _E. r. simulans_, in keel proportionally lower, tip proportionally shorter, distal 1/5 of shaft less laterally compressed, shaft usually longer; from _E. cinereicollis_, in angle formed by tip and shaft smaller, shaft shorter, ridges on either side of tip distinct; from _E. quadrimaculatus_, in tip proportionally longer, shaft usually shorter; from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base not markedly widened, shaft longer, angle formed by tip and shaft larger. For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E. sonomae_, _E. amoenus_, _E. dorsalis_, _E. merriami_, and _E. quadrivittatus_, see the accounts of those species. Baculum of _E. r. simulans_: Shaft thick; keel proportionally low, 2/5 of length of tip; tip 40 to 48 per cent of length of shaft; angle formed by tip and shaft 130°; distal 2/5 of shaft laterally compressed; base slightly wider than shaft; shaft medium to long, 3.30 to 4.26 mm. Differs from _E. cinereicollis_ in, keel proportionally higher, shaft shorter, tip proportionally longer, angle formed by tip and shaft smaller, distal 2/5 of shaft more laterally compressed; from _E. quadrimaculatus_ in, keel proportionally higher, angle formed by tip and shaft larger, tip proportionally longer, distal 2/5 of shaft more laterally compressed, shaft shorter; from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in base not markedly widened, shaft usually longer. For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E. sonomae_, _E. amoenus_, _E. dorsalis_, _E. merriami_, and _E. quadrivittatus_, see the accounts of those species. The differences between the bacula of the subspecies _Eutamias ruficaudus ruficaudus_ and _E. r. simulans_ are comparable to those usually found between species of chipmunks. Consequently, I suspect that _E. r. simulans_ and _E. r. ruficaudus_ are specifically distinct and suggest that a search would be worth while for specimens in the geographic area between the geographic ranges as now known for the two kinds to ascertain whether intergradation (the criterion of subspecies) occurs. I suppose there is no intergradation but in the absence of precise information, I choose not to modify the current taxonomic arrangement of _E. r. ruficaudus_ and _E. r. simulans_. _Specimens examined_: 17. _E. ruficaudus ruficaudus_: Montana: _Flathead Co._: 1 mi. W and 2 mi. S Summit, 5,000 ft., 2. _Ravalli Co._: Big Hole Hill, 6,000 ft., 2; Big Hole Hill, 6,600 ft., 1; Continental Divide, Big Hole Hill, 7,000 ft., 1. _E. r. simulans_: Idaho: _Bonner Co._: Priest Lake, 1 (BS). _Kootenai Co._: 13 mi. E and 5 mi. N Coeur d'Alene, 3. _Shoshone Co._: Mullan, 1 (BS). _Clearwater Co._: 25 mi. E and 16 mi. N Pierce, 6. #Eutamias cinereicollis# (J. A. Allen) Figure 13 General tone of upper parts dark grayish tawny; size medium to large; skull large; braincase widened. Baculum: Shaft thick; keel proportionally low, 1/5 of length of tip; tip 34 per cent of length of shaft; angle formed by tip and shaft 145°; distal 1/3 of shaft slightly compressed laterally; base slightly widened; shaft long, 4.88 mm. Differs from _E. quadrimaculatus_, in keel lower, ridges on either side of tip weakly developed, angle formed by tip and shaft larger; from _E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in shaft longer, base not markedly widened, angle formed by tip and shaft much larger. For comparisons with _E. alpinus_, _E. minimus_, _E. townsendii_, _E. sonomae_, _E. amoenus_, _E. dorsalis_, _E. merriami_, _E. quadrivittatus_, and _E. ruficaudus_, see the accounts of those species. _Specimen examined_: One from Mount Thomas, White Mountains, Apache Co., Arizona (BS). #Eutamias quadrimaculatus# (Gray) Figure 14 General tone of upper parts bright reddish; pattern inconspicuous; light and dark facial stripes strongly contrasting; size large; skull relatively small and slightly built. Baculum: Shaft thick; keel relatively low, 1/4 of length of tip; tip 27 per cent of length of shaft; angle formed by tip and shaft 120°; distal 1/3 of shaft slightly compressed laterally; base slightly wider than shaft; shaft long, 4.35 to 5.28 mm. Differs from _E. speciosus_, _E. panamintinus_, _E. townsendii_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_, in shaft markedly longer; base not markedly widened; angle formed by tip and shaft larger; tip proportionally shorter. For comparisons with all other species of chipmunks from western North America, see the accounts of those species. _Specimens examined_: 4. California: _Plumas Co._: Mountains near Quincy, 1 (BS). _Placer Co._: Blue Canyon, 1 (NM). _Alpine Co._: Markleeville, 1 (BS); N fork Stanislaus River, 1 (BS). #Eutamias speciosus# (Merriam) Figure 15 General tone of upper parts bright; light and dark elements of color pattern strongly contrasting; outer stripes broad and strikingly conspicuous; size medium; skull moderately broadened; dorsal outline of skull strongly arched in profile; upper incisors short and sharply recurved. Baculum: Shaft thick; keel of medium height, 1/3 of length of tip; base of keel 1/3 of length of tip; tip 47 to 55 per cent of length of shaft; angle formed by tip and shaft 90°; distal 2/3 of shaft markedly compressed laterally; base markedly wider than shaft; shaft short to medium, 2.11 to 3.17 mm. Differs from _E. panamintinus_, in base of keel proportionally shorter, angle formed by tip and shaft smaller; from _E. umbrinus_ and _E. palmeri_, in keel higher, angle formed by tip and shaft smaller, distal 2/3 (not 1/2) of shaft markedly laterally compressed, base markedly wider; from _E. bulleri_, in keel smaller, shaft shorter, tip proportionally longer, ridges on either side of tip distinct. For comparisons with all other species of chipmunks of western North America, see the accounts of those species. The baculum in _E. speciosus frater_ is approximately the same size as in _E. umbrinus inyoensis_, but differs in shape as described above. _Specimens examined_: 6. _E. speciosus frater_: California: _Madera Co._: San Joaquin River, near head of N fork, Sierra Nevada Mountains, 2 (BS). _E. speciosus sequoiensis_: California: _Tulare Co._: Mount Whitney, 1 (BS); Sequoia National Park, 2 (BS). _E. speciosus callipeplus_: California: _Kern Co._: Mount Pinos, 1 (BS). #Eutamias panamintinus# (Merriam) Figure 16 Dorsal dark stripes reddish; size small to medium; skull of medium size; braincase flattened. Baculum: Shaft thick; keel low, 1/3 of length of tip; base of keel 1/2 of length of tip; tip 52 per cent of length of shaft; angle formed by tip and shaft 110°; distal 2/3 of shaft moderately compressed laterally; base markedly widened; shaft short, 2.17 mm. Differs from _E. umbrinus_ and _E. palmeri_, in distal 2/3 (rather than 1/2) of shaft moderately compressed laterally; from _E. bulleri_, in keel smaller, shaft shorter, ridges on either side of tip distinct. For comparisons with other species of chipmunks of western North America, see the accounts of those species. The structure of the baculum most closely resembles that of _E. speciosus_ and the geographic ranges of these two species are in juxtaposition. _Specimen examined_: One from Coal Kilns, Panamint Mountains, Inyo Co., California (CN). #Eutamias umbrinus# (J. A. Allen) Figures 17-18 General tone of upper parts dark; size medium to large; skull of medium size; braincase narrowed. Baculum: Shaft thick; keel low, 1/4 of length of tip; tip 36 to 50 per cent of length of shaft; angle formed by tip and shaft 100°; distal 1/2 of shaft markedly compressed laterally; base markedly widened; shaft short to medium, 2.51 to 3.03 mm. Differs from _E. bulleri_, in shaft shorter, keel smaller, ridges on either side of tip distinct; distal 1/2 of shaft strongly compressed laterally. Does not differ from _E. palmeri_. For comparisons with all other species of chipmunks of western North America, see the accounts of those species. Specimens of _E. umbrinus montanus_ from north-central Colorado have, in the past (Howell 1929:82), been referred to _E. quadrivittatus quadrivittatus_. In many features these two kinds of chipmunks resemble each other closely; their bacula, nevertheless, differ markedly (compare figs. 8-9 with 17-18). _Specimens examined_: 25. _E. umbrinus umbrinus_: Wyoming: _Uinta Co._: 10 mi. S and 1 mi. W Robertson, 8,700 ft, 1. Utah: _Uintah Co._: Paradise Park, 21 mi. W and 15 mi. N Vernal, 10,050 ft., 12. _E. u. adsitus_: Utah: _Beaver Co._: Britts Meadow, Beaver Range Mountains, 8,500 ft, 1 (BS). _Wayne Co._: Donkey Lake, Boulder Mountain, 10,000 ft., 1 (UU). _Garfield Co._: Wildcat R. S., Boulder Mountain, 8,700 ft., 1 (UU). _E. u. sedulus_: Utah: _Garfield Co._: Mount Ellen, Henry Mountains, 1 (BS). _E. u. inyoensis_: California: _Tulare Co._: Mount Whitney, head of Big Cottonwood Creek, 2 (BS). Nevada: _Elko Co._: W side Ruby Lake, 3 mi. N Elko County Line, 1. _E. u. nevadensis_: Nevada: _Clark Co._: Sheep Mountains, 1 (MM). _E. u. fremonti_: Wyoming: _Sublette Co._: 31 mi. N Pinedale, 8,025 ft., 1; 19 mi. W and 2 mi. S Big Piney, 1. _E. u. montanus_: Colorado: _Boulder Co._: 3 mi. S Ward, 9,000 ft., 1; 1/2 mi. E and 3 mi. S Ward, 9,400 ft., 1. #Eutamias palmeri# Merriam Figures 17-18 General tone of upper parts grayish tawny; ocular stripe pale; skull, rostrum, nasals, and upper incisors shorter than in _E. umbrinus_. Baculum: Indistinguishable from that of _E. umbrinus_. This supports the opinion of previous students that _E. palmeri_ is a close relative of _E. umbrinus_ which occurs immediately to the north and east. Intergradation does not occur between these two species, for, low-lying terrain, inhospitable to chipmunks, isolates _E. palmeri_ from its relatives. (Verbal information from E. R. Hall.) _Specimen examined_: One from Charleston Peak, 8,000 ft., Clear Creek Co., Nevada. #Eutamias bulleri# (J. A. Allen) Figure 19 General tone of upper parts dark; dorsal dark stripes conspicuous and black; size large; skull large. Baculum: Shaft thick; keel high, 1/2 of length of tip; keel long, 1/2 of length of tip; tip 40 to 48 per cent of length of shaft; angle formed by tip and shaft 100°; base markedly widened; shaft of medium length, 3.30 mm. For comparisons with all other species of chipmunks of western North America, see the accounts of those species. The large size of the keel of the baculum in this species is distinctive among chipmunks of western North America. _Specimens examined_: 2. _E. bulleri bulleri_: Zacatecas: Sierra de Valparaiso, 2 (NM). [Illustration: FIGS. 1-19. Lateral view of right side, unless otherwise indicated, of the baculum in each of the species of chipmunks (subgenus _Neotamias_) of western North America: 1. _Eutamias alpinus_, No. 12577 CN; from Big Cottonwood Meadow, Tulare Co., California. 2. _E. minimus consobrinus_, No. 25439; from 13 mi. S and 2 mi. E Robertson, 9,200 ft., Uinta Co., Wyoming. 3. _E. townsendii cooperi_, No. 53169; from Brooks Meadow, 4,300 ft., 9 mi. ENE Mt. Hood, Hood River Co., Oregon. 4. _E. sonomae sonomae_, No. 98436 BS; from Redding, Shasta Co., California. 5. _E. amoenus luteiventris_, No. 33811; from 7 mi. W West Yellowstone, 7,000 ft., Fremont Co., Idaho. 6. _E. dorsalis dorsalis_, No. 213415 BS; from 3 mi. N Ft. Whipple, 5,000 ft., Yavapai Co., Arizona. 7. _E. merriami merriami_, No. 1270 LA; from Mount Pinos, Ventura Co., California. 8 and 9. _E. quadrivittatus quadrivittatus_, No. 35648/47919 BS; from Canon City, Fremont Co., Colorado. Figure 9 in dorsal view. 10. _E. quadrivittatus hopiensis_, No. 783 UU; from Moab, 4,500 ft., Grand Co., Utah. 11. _E. ruficaudus ruficaudus_, No. 33884; from 1 mi. W and 2 mi. S Summit, 5,000 ft., Flathead Co., Montana. 12. _E. ruficaudus simulans_, No. 41478; from 13 mi. E and 5 mi. N Coeur d'Alene, Kootenai Co., Idaho. 13. _E. cinereicollis cinereicollis_, No. 208621 BS; from Mount Thomas, White Mountains, Apache Co., Arizona. 14. _E. quadrimaculatus_, No. 95780 BS; from Mountains near Quincy, Plumas Co., California. 15. _E. speciosus sequoiensis_, No. 29135/41203 BS; from Mount Whitney, Tulare Co., California. 16. _E. panamintinus panamintinus_, No. 12502 CN; from Coal Kilns, Panamint Mountains, Inyo Co., California. 17. _E. umbrinus umbrinus_, No. 38062; from Paradise Park, 21 mi. W and 15 mi. N Vernal, 10,050 ft., Uintah Co., Utah. 18. _E. umbrinus montanus_, No. 20105; from 1/2 mi. E and 3 mi. S Ward, 9,400 ft., Boulder Co., Colorado. Dorsal view. 19. _E. bulleri bulleri_, No. 193142 NM; from Sierra del Valparaiso, Zacatecas.] DISCUSSION In California, Johnson (1943) recognized ten species of chipmunks and assigned these to the five main groups of species which were proposed by Howell (1929). In characterizing each species, Johnson (_op. cit._) not only made a careful study of skins and skulls, but also employed many ecological data. Study of the bacula of the Californian chipmunks supports Johnson's (_op. cit._) conclusion that there are ten species, but suggests that there are three (not five) groups of species in California--as well as elsewhere within the geographic range of the subgenus _Neotamias_. The three groups are (see figs. 1-19): 1. _minimus_-group (_E. alpinus_, _E. minimus_, _E. townsendii_, _E. sonomae_, _E. amoenus_, _E. dorsalis_, and _E. merriami_); 2. _quadrivittatus_-group (_E. quadrivittatus_, _E. ruficaudus_, _E. cinereicollis_, and _E. quadrimaculatus_); and 3. _speciosus_-group (_E. speciosus_, _E. panamintinus_, _E. umbrinus_, _E. palmeri_, and _E. bulleri_). _Eutamias panamintinus_, according to Howell (_op. cit._:78) and Johnson (_op. cit._:83), is a near relative of _E. amoenus_. But, the baculum in _E. panamintinus_ more closely resembles that in _E. speciosus_ than that in _E. amoenus_ (compare figs. 5, 15, and 16). Consequently I have placed _E. panamintinus_ in the _speciosus_-group. In north-central Colorado, specimens that really are _E. umbrinus_ (subspecies _montanus_) have, in the past (Howell _op. cit._:82), been referred to _E. quadrivittatus quadrivittatus_, but the bacula of the two species differ markedly from each other (compare figs. 8-9 with 17-18) and permit the specimens readily to be correctly identified to species. Further, Howell (_op. cit._:95) placed _E. umbrinus_ (subspecies _umbrinus_ and _fremonti_ of current usage) in the _quadrivittatus_-group, whereas the structure of the baculum leads me to place _E. umbrinus_ in the _speciosus_-group. Thus, groups of species established on the basis of only skulls and skins, in a few instances differ from those established on a broader basis which includes the bacula. Johnson (_op. cit._:63) writes, "Each species [of Eutamias] has a characteristic habitat which differs from those of other species. Where two or more species occur together in a general locality they are usually mutually exclusive in their choice of foraging and nesting sites and in the time of breeding." Thus he classified the species of Californian chipmunks not only by morphologic characteristics but by habits and habitats as well. The characteristics of the skulls and skins of chipmunks probably reflect the habitats in which these animals live. The characteristics of the bacula, on the other hand, may also reflect the habitats in which the animals live, but to a lesser degree. Because the structures of the bacula are probably less affected by the action of the external environment they probably indicate relationships between groups of species of chipmunks more clearly than do characteristics of the skulls and skins. If the structures of the bacula indicate relationships between groups of species of chipmunks more clearly than do the characteristics of the skulls and skins, the close resemblance of the skulls of _E. quadrivittatus_ and _E. umbrinus_ may be thought of as convergence. The same can be said of _E. amoenus_ and _E. panamintinus_. LITERATURE CITED FRILEY, C. E., JR. 1947. Preparation and preservation of the baculum of mammals. Jour. Mamm., 28:395-397, 1 fig., December 1. HOWELL, A. H. 1929. Revision of the American chipmunks (genera _Tamias_ and _Eutamias_). N. Amer. Fauna, 52:1-157, 10 pls., 9 maps. JOHNSON, D. H. 1943. Systematic review of the chipmunks (genus Eutamias of California). Univ. California Publ. Zool., 48:63-148, 6 pls., 12 figs, in text, December 24. WHITE, J. A. 1951. A practical method for mounting the bacula of small mammals. Jour. Mamm., 32:125, February 15. _Transmitted June 26, 1953._ 24-8968