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[From the Quakterly Journm, of the GRorooiCAi. Society /o 
 
 November 1870. J 
 
 NOTES 
 
 ON SOME SPECIMENS OF 
 
 LOWER SILURIAN TRILOBITES. 
 
 E. BILL TNG 8, Esq., F.G.S. 
 
 I'AL/KONTOLOGIST OF THE 6E0L0OICAI. PIJRVK . vy CANADA 
 
 (Platbs XXXI. As» XXXII.) 
 
 1. Asfjphus platycephalus, with sonie of the le<js preserved. 
 
 Tnra specimen was collected in the Trenton Limestone, at the city 
 of Ottawa, about ten years ago. When disedvered it wa.s Kirig Hat 
 njion a thin slab of liniestone, and well preserved, witli the ex- 
 ception of the eyes, which seem to have been ll)rc(;d inwards by 
 pressure from above. It was also diviih^d into two pieces by a 
 tisstiie Avhich extended diftjj;<mally across, from the first segment 
 of the thorax on tin* left side \o the fifth seg7nent on the riglit. 
 
 It remained in the Museum for several years without attracting 
 ])arti<ular attention, until one day, observing that the part in front 
 of the tissiire wat* somewhat loosely attached, I removed it, and was 
 surprised at finding, on the underside, not oidy the hypostoma in 
 place, but also what appeared to be some of the legs of the animal. 
 As the ])art behind the fissxire was men; firmly attached to the 
 stone, I had it cut across just behind the eighth segment by the 
 lapidary of the Survey. The remainder of the thorax was then 
 easily split off. The pygidium came otf with difficulty and in two 
 pieces. All the pieces were Ihen fiustened together; and we thus 
 obtained two specimens, one of which show.s the underside of the 
 Trilobite, tiiul (he other its impression on the stone. 
 
 Un the underside (Tl. XXX I. fig. I) m broad shallow groove extends 
 
 « 
 
(3X) 
 
 480 
 
 PROCEEDIKOS OF THE GEOLOGICAL SOCIETY. [May 11, 
 
 from the spaco botwren tlic two lobop of the hj'pofitoma, whero wo 
 must .suj)poso tho mouth to b" situated, baolswards along the median 
 line to tlie pygidium. Tliis coiicsponds in position to the sternum 
 of tlie ordinary orustaoea. The U'gs are arranged in eight pairsr. tho 
 l)aseH of eacJi ]»air being situated exactly under one of the eight seg- 
 ments of the thorax, and at the sides of the sternal groove. 
 
 The legs of the tirsi pair are better- preserved than the others. 
 They curve forAvardis and eaii lie traeed to a point nearly under the 
 outer edge of the eye, or, rather, between the eye and the outsidi' »i 
 tho head. The otlier seven pairs follow at the average distanec of 
 two and a half lines from eaeh other. The eight pairs thus occupy 
 about twenty lines of tlio h ngth of the ventral surface. This is 
 exactly the length of the thorax, measured on the upperside. This 
 trilobite has always eigbt segments in the thorax ; and there is thus 
 on the underside one pair of ai>p<'ndag(!8 to vAich segnuint. Although 
 some of them are veiy imperfect, and the portions tliat remain are 
 somewhat displaced, with a little study of tho specimen it can be 
 seen that they all curve forwards, and arc thus, most probably, am- 
 bulatory rather than natatory h'gs. 
 
 There appear to be several joints in each of these appendages; but 
 the exact number cannot be made out. On the left side, the first 
 four legs show very clearly that there are at least two, one at five 
 lines from the side of the groove, and another about three lines fur- 
 ther out. The position of eaeh of these is indicated by a small protu- 
 berance (PI. XXXI. fig. !,)()• On the right side the preserved jtortions 
 of the legs are longer, and thus indicate a greater number of arti- 
 culations, although they canrot be distinctly seen. I think that 
 each leg consist(Hl of at least four or five articuhitions, 
 
 On the pygidium there are three small ovate tubercles, arranged 
 in a line, that i ""em to be organic (fig. l,d); and if they are so, they 
 are, perhaps, the processes to which respiratory feet Avere attached. 
 
 The length of the specimen is four and a half inches, and tho 
 width two and a half inches. On a side view the height of the 
 head just behind the eye j is nine lines, and at the middh- of tho 
 thorax about seven lines. The depth of the internal cavity at the 
 back part of tho head is seven Hues, and at the last segment of tho 
 thorax four lines. The plane in which the legs are situated is 
 therefore not so low down as the extremities of the pleune. The 
 visceral cavity is thus about one-third less than the whole bulk of 
 the animal (Vl XXX II. fig. 1). 
 
 The above is all that I desire to say at present concerning this 
 remarkable .spt^inien. The first and all-important point to be de- 
 cided is, whether or not the forms exhibited on its underside are 
 truly, what thoy appear to be, locomotive organs. If this question 
 be decided in the atfirmative, it will then remain for Oarcinologists 
 and othi-rs to homologize them Avith the limbs of existing Crustacea. 
 It is scarcely necessary to remark, in this place, that, in view of 
 the great zoologieal questions that are at present being discussed, 
 the correct determination of the affinities of the Trilobit(»8 is of ex- 
 traordinary importance. 
 
1870.] 
 
 U1LLIN09 — LOWER-SILUUIAN TK1L0BITK8. 
 
 4«1 
 
 A Khort notice of the spi'cinKJii was drawn uj) and read liotbro the 
 Natuial-ltislory Society ot'Montreal iti 18<)4. IMihlicutioii, however, 
 was (Icl.'iyed, partly because 1 hoped to ot)tain addiliouul (.'vidence, 
 but principally heenusc I wished to have tlie s])ecim»m first exhi- 
 bited tc) the (ieological Socii^ty, and examined by .is many of the 
 Fellows as possible-. Feelinfj; somewhat a]t]»rehtnsiv(f that it would 
 be ditlicidt to pcrsuad*' geolo^;ists and ])aheinitolo}}:ists into tlu^ belief 
 of the existence of tiilobitic le.n's by tijrures and descriptions alone, 
 I thouffht it better to wait until the [)apcr and the specimens could 
 be laid before tlie So(!iet} at the same time. 
 
 During the six years thai have elapsed, a vast number of Trilo- 
 bites have passed thron<j:h my hands, but nearly all of them in a 
 frafrmentar} eonditioTi. Among such, 1 am satislied, we may seek 
 in vain for any traces of locomotive organs. We can only expect 
 to tind tlieiu in ])erfect or nearly peif'Ct specimens. These latter, 
 considering the prodigious multitude o{ these animals that must 
 have existed in the Silurian and Devonian soas, are not abundant 
 fossils ; at least they are not so in our Canadian rocks. For ex- 
 ura])le, during the twenty years that 1 have colkcted fossils, I do 
 not believe th 'it F have seen tifty ajteciinens of ^4. plat tic''p!i(if its with 
 Avith the head, thorax, and pygidium all in connexion. \Vc have 
 had a munber of those belonging to the jnovincial collection cut up 
 and polished, without any success whatever. They were not the 
 l>est ones, but they were as perfect as was the subject of this notice 
 b(!fore it was split apart. There are others in the collection whi' h 
 may have the underside preserved ; but avc do not like to Hacnlice 
 them. Although no additional evidence of the existence o .mbs 
 was discovered, several points in the structure of other pai w<;re 
 ascertained, which will be described further on. As Sir W. E. Lo- 
 gan is about visiting London, and has kindly offered to take charge 
 of this ]ia]H'r, and will also take the specinu^ns with him, I shall 
 delay publication no longer. 
 
 2. Diacoverij of the Fandenan Organ* in several American apedes 
 
 of Asu])hus. 
 The evidence afforded by the spticimen above described, and others 
 of which T have made sections, proves that in the genus Axophits 
 the underside was not tlat, but soinewh".t concave. In the head, ou 
 each side of the mouth, then; was a cavity like that which occurs in 
 the existing king crab — Llmnhis Pohqiht ntus. The position of these 
 cavities is at e c, in VI. XXXL lig. J. They arc partially filled uj) 
 in the specimen ; but I havi- ascertained their depth to be about five 
 lines in another individual of the same size. The ends of the 
 plei'-iO) projected downwards a short distance below the level of the 
 sternum. The pygidium was also concave at the sides, with a por- 
 tion along the middle, holding the intestiiKS convex. This structure 
 can be seen, in part, by examining the slab from which the specimen 
 
 * Dr. Volbortli rnlls tlie organs ii: qiiostion "<//> I'liMhrfcfun Ort/ane," a term 
 of which T hciirtily approve, us. if fionordly adoyttod, it will permanently asso- 
 ciate Dr. Pander s liamc widi his discovery. 
 
482 
 
 PB0CBRDIN08 OF THR GKOLOQICAL 80CIKTT. [May 1 1 , 
 
 above noticed waa split. Portions of the lower niarg;in» ol' the head 
 and tail, and the extremities of some of the pleune, reraiiinod stick- 
 ing in the stone. It can also he proved by polished sections throuifh 
 the head and tail of any well-preserved specimen. Such seciions 
 usually show that a portion of the crust, called the " doublure " by 
 Barrande, all round the margin is folded under and reflected upwards, 
 ending in a free thin edge (PI. XXXI. figs. 2, 3, 4). The plcurie 
 have tdso a doublure, which extends upwards, nearly halfway to the 
 median Icbe of the body. In conse^iucnce of this structure the ex- 
 tremities of the pleurae are hollow, exactly like those of a lobster. 
 
 In Lhnulus a similar doublure occurs ; ajid we can see thrae that 
 it is continuous with the thin membranous crust which eovers the 
 underside of the body and bears the limbs. Eetwccn the sternum 
 of Limulus, with its load of ponderous legs, and the doublure there 
 is no connexion, all round, excej)t this fragile membrane. In con- 
 sequence of this structui'e it often comes away with all its appen- 
 dages, leaving nothing of the animal except its huge earapuce, 
 pygidium, and telson. Specimens of this great crab in this condi- 
 tion arc oommon in museums. 
 
 In the geiuis Asaphm, and, no doubt, iu all other Trilobites, the 
 doiiblure is, as in these ira]»erfecti specimens of Lhtmlns, only the 
 remains of the integument M'hieh covered th<* und(;rside and sup- 
 ported the sternum. These two genom, however, differ widely in 
 other respects. 
 
 The doul^luro of A. platycephalus was figured by Dr. Bigsby so 
 long ago as 1823, in the Geological Transactions, 2nd series, vol. i. 
 pi. xxvii. fig. 1 e, among the illustrationf of his paper " On the (ieo- 
 graphy and Geology of Lake Huron." The figure shows a section 
 through the doublure on the right side, just in front of a line dravvii 
 across the head through the centres of the eyes. In the description 
 of the figure the true character of the part in (juestion is recog- 
 nized, by the remark that '* the shelly crust of the tmder side Joins 
 the upper at the sides.-' It is also shown in fig. 1 b, on the same 
 plate, which represents the underside of the same specimen, with 
 the hypostoma in place*. In that paper this now famous Trilobite 
 
 * Tills is the second hypostoma ever figured. Barrande, in his great work on 
 the Trilobitesof Bohemia, comraonces the history of the organ in question, thus: — 
 
 " A.. Iktnn{e» Hisforiques. 
 
 " 1821. Leplus ancien liypostome connu, est Sgur6 et d<5crit par Wahlenberg, 
 sous le nom de EniomostracUes bi'cephalm (Nov. Act. Soo. Sci. Upsal, viii. '67, 
 pi. i. flg. 6). 
 
 " 18'22. Ch. Stokes d^couvre sous la t^te d'Asaphus platr/ccphalus (^Tsofelus 
 gigas, De K.) une pittoe cpustacee. plac6p a I'entree dti restomac; et il lu deerit 
 d ms les Transact. Geol. (nouv. ser. i. 208, pi. 27). 
 
 " La mfime ann^, le savant Am^rictiin D*' Kay deerit et repr^sente lo m'^me 
 appareil que nous retrouvons figure par Buckland dans les Bridgew. Treatises, 
 en 1837." (Barmnde, Systenic Silurien tfec. vol. i. p. 1.54.) 
 
 There is a difficulty about the nomenclature of tliis Trilobite, owing, in part, 
 to some uncertainty as to the true dates of publication. In the later rejKjrta of 
 our survey we have adopted the name given to it by Stokes, while most American 
 authors call it either Asu jhas gigns or Im)telus gigas. Dr. Bigsby'e paper woe 
 
187(». 
 
 lUI.UNOS — I,OWI.U-SirUKlAN XRILOUriKS. 
 
 483 
 
 WPS first iniidci known to scionco. It was named by Mr. Stokos. 
 Very nunieioiis Hf^urrs of the doublnrc of iliffi-n iit sjiccios of Tiilo- 
 bitos may Ix' Het*n in tht' !ary;i' worku of i{)irr!in<lf, SultiT, and 
 otlitTs; but it is ili'scrihrd liy soin"' jis ;i ])ortion o*' the crust, fuldcil 
 nmU'v to |j:iv<' i^n.'.itcr strt'iif;tli tn tin- inarj^ins of the licad and tail. 
 'J'his, however, is not the wlmlc of its inlcriirctiition. It is (as 
 !dtoV(> slated) ;i part of tlw nndorside, which, on account of its greater 
 thickness and hardni^ss, is iisiniUy i)reserved, while the more mem- 
 br;uious and frajj;i]e ))!irtioiis have disap])«>ar(Ml. 
 
 About twcUt' years iv^>, Dr. I'auder discovered Bome small scars 
 and tiiliercles on the inner surface of the doublure of the Unssian 
 Trilobitc^l. t.rpifnsHs ; and th(>y were afterwards described and figured 
 by J)r. A. Vdborth in several papers*. He supj)ose8 thera to indi- 
 cate the ]K>ints of attachment of s(jft swimming-feet. EichAvald has 
 also described and figured the sarao organs in A. ScJiIothelvul, but 
 maintains that they are the sor-kets of the first segments of hnrd. 
 horny, articulated, ambulntory legst. These two distinguished 
 naturalists have discussed the points in difference between them at 
 length, find with their well-known ability, in the works cited below. 
 I have discovered the same orgnns in three of our species— J . 2>/«- 
 tijcephdlus, A. I- made)) s Us, and A. mcf/iston. They are smnll re nnded 
 or ovate scars, with an i-levated protuberance on one .side. They 
 are situated on the doublure, close to the anterior margins of the 
 pleuric. The protuberance leaves a small but distinctly marked pit 
 in the cast of the interior, as is shown in PI. XXXI. fig. 5. That 
 organs of some kind were here attached, I think there can be little 
 doubt. But what was their function ? If tln^y were legs, then 
 Amphiis must have had four paralJel rows of limbs Ixiueath the 
 thorax. Tf the two inn(T rows were ambulatory, as I supiios(! those 
 of our Trilol)ite to have been, then the two outer rows may have 
 been natatory, as Dr. Volborth maintains. Eichwfihl figures several 
 slender articulated organs, which he supposes to be the legs of Tri- 
 lobites ; and indeed they resemble, not remotely, those of onr spe- 
 cimen. For convenience of refereiice, I have copied his figures 
 (Plate XXXI. fig. fi). If they are tndy the same organs, he would 
 still be, to some extent, wrong ; for he thinks they were attached 
 to the doublure. 
 
 r«wl February 21st, Mardi 7t}i, and 2l8t, 1823. Tt is usually cited under the 
 diite of JS22. In his article on the Minerals and Fos.'^ils of Canada, pubhslied 
 in Sillinmn's Journal in 1^24, vol. viii. p. 84, he alludes to it thus: — "I beg to 
 refer to three figures of large utiknowii trilobites, published last year in tiio 
 Geological Transaetions of London.'' T in er from this that the portion of the 
 Transactions contjuning hispap.T was issued in 182.'i. De Kay's pa))er. in wliieh 
 the species was first ealled Iso/r/us (/{(/iii, was reatl before [ho New York L}'e*uin 
 of Natural History, October 27th, 182;{. It is generally quoted with the date 
 1824. 
 
 * (1) Deutsche Petcrsb. ,\kad. Zeitung, 18,")7, No. 25.") ; (2) Verhandl. der 
 kaiserl. nuner. Geaellsch. Jahrg. 18.')7 o8. p. ir»8; (.'{) Mein. Aead. Tnij). St. Pe 
 tersbourg, tome vi. No. 2, I8(;.'}; (4) Bull. Soc. Imp. Nat. Moscou, No. 1, 1800. 
 1 have only seen the last two of these. 
 
 f Lotbaa Rossica, vol. i. pt. 2. p. iyi»4, pi. 02. Gg. 24. 
 
4M 
 
 I'liOCKKDINUS OK THE 0EOI,O(}I(AI, HOriT.TT. 
 
 May 1 1 , 
 
 3. Are Proti(hi\it»H awf C'liniiifticliTiitcs the trnch of Tn/ohife»? 
 
 In his (Irsorifilioii of /'rotidnites, Prof. ()"en Hays :— " Tlic 
 LlnmlvH, -vvliicli hfis the siiir.ll anterior j)air ol' limbs (wnr th(^ 
 niiddlo lino) uul Iho next four lateral jjairs of linilm hifurcatf 
 at tlu; fret' extremity, the last ■ pair of latt'i.il linihs with lour 
 iura<'llil'orm apjiendupeH, and a long slender hard tail, <;ome8 the 
 nearest to my idea of the kind of anijnal \vliieh has left the im])res- 
 Bions on the Potsdam sandstone''*. In 1M(;2, J)r. .1. VV. Dawsou 
 lusted this opinion hy actual experiment, on a sandy beach near (ho 
 mouth of the Scarhoronph river, on tlio coast of Maine. Having 
 eauglit a LhnvhiS he kept it nlivc for seVJTal days, and " tried its 
 m''>do v»f locomotion under various couditions on the sandy shore, and 
 presei-ved sketches of the markings "t. His figures and descriptions 
 prove dearly that the track;? on the sandstone could have lu'in made 
 by an animal having a structure like that oi Llmnlvr.. The grooves 
 along th(; sitlo of the track vere made by the (>dge8 of tlu* broad 
 teplialothorax, the small pit-like impressions by the extremitits 
 of the larg<' limbs, the transverse grooves by the lanielliform feet, 
 and the median groove by the telson. If it be grant( il ihnt^lsaji/ms, 
 in addition to its thoracic legs, possessed a set of lamellar .^wimming- 
 appcndages under the pygidium, then Uie struetuns ofthonnder- 
 surfuce would be sufficiently like that of Lhnu/us to enable it to 
 l)roduce the same markings. The median groove m'., be made by 
 a Trilobite Avith a caudal s])ine like that of Meiiahiapis hi ros ( A ngelin ). 
 This species is a irxn} A-sophus. The large Trilobite of the I'otschim 
 sandstone, Dikehnephahiiii, differs littli- in general structure from 
 Atifiphns, while the ])ygidium of several of the species evin(>es a ten- 
 dency to become spinous around the margin. The genus A'jlii!>jtis 
 (Hall) ap])ears to me to be a Tiilobite of the same group; and, more- 
 over, the specimens iigured seem to lie the tail ind not the head. 
 Wliat are 8npp(»sed to be the t^yes are the bases of two spines, like 
 the one that occurs on the pygidium oi Buthyurus sjHniyer (Ackhis- 
 pis spinlitef, Hall). 
 
 Dr. Dawson, after comparing all the facts, says: — "On the whole 
 we may safely coiiclude that, if any of the larger primordial Trilobites 
 wore provided with walking- and swimming-leet of the type of 
 those of Linndns, but differing in tletails of structure, they may have 
 produci^l both the Protlchnltct, and tlu! Cihnarfichnites.'" Prof. 
 J. I). Dana, also speaking of the latter, says; — "It has been re- 
 garded as the track of a very largo (iasteropod ; but it is (juite as 
 probable that it was made by the clusters of foliaceous aj)pendageH 
 of one of the great Trilobites — these a])pendages being its locomotive 
 organs''^. Tho following, therefore is the present state cf the ques- 
 tion : — 
 
 1. The tracks cotild have been made cither by a rjmvh(s or by a 
 Trilobite. 
 
 * Quart. Jonrn. Geol. Soc. vol. viii. p. 224. 
 
 + t'liimdian Nuturalist and Geologist, vol. vii. p. 27(3. 
 
 I Manual of Geology, p. 18."). 
 
18V0.J 
 
 BTT.MVns — LOWEH-SIIiURIAJr 'rKiXOnn'KS, 
 
 485 
 
 2. No fossils of the order ( Xlphosura) to <vhiih Limulus belongs 
 havi' been found so low down as the I'otsdain siuidstoue. 
 
 '». Largc^ Trilohitos occur there in ubuiulanco. 
 
 riio wei^iht of the evidence, tlierefore, favours (he 'nion that 
 the tracks in (jncHtion are tho le of Trilobites. It is important to 
 bear in luind that I'rotii'hniteit and Cluiiactlchnites occtxr togdlie'" on 
 the hanie slabs of i^and-itoue. Dr. ])a\vson's observations, clearly 
 prove that both might havf been made by an animal of tho same 
 species under ditFcrciiit circumstances, accordingly as its walking- or 
 its swinmiing-feet were made use of. Judging from tho width of 
 the tracks, 1 b(;lit>vc that several of those of both kinds oji one of the 
 slabs, now in the Muaeuui of the Survey, were made by the same 
 imlividual. 
 
 4, On a roUed-up specimen o/Talymone scnaria^Z^^c? mlh small 
 
 ovate fiodii's. 
 
 It is above stated that whde seeking for additional evidence re- 
 lating to the limbs of 'frdobites, a number of specimens were cut up 
 and jxilished. One of these was an exceedingly perfect, rollcd-np 
 CaJiimene senaria, from the Hudson-lliver group at Cincinnati, in 
 Ohio. 
 
 This animal (PI. XXX 11.. fig. H) appears to have shut itself U]» so 
 coin[)lett'h' that the fine mud in wiiich it was buried could only 
 gain access througli the small fissure at </, where tho points of the 
 head and tail come together. There is here a small space, within 
 the letters, c, d, e, f, which is of a light j-ellowish brown. 1 think 
 that neither the mud, iu>r even the muddy water, penetrated fur- 
 ther. There is ni» trace of comminuted fossils in this space, as there 
 is in moat specimens that 1 have cut up. The whole of the re- 
 mainder of the cavity is tilled with a greenish-grey spar, with a 
 patch in the back part of the Jiead at h of a ditFerent colcmr. This 
 Bpar holds a vast number of small ovate bodies (fig. 4), of which the 
 greater diamet(>r is about an eightieth of an inch, and the lesser a 
 hundredth. They ar(.i of a lighter colour and more opaque than tho 
 matrix. When examined with a good glass, and under favourable 
 light, they seem to float, as it were, in the spar. The hypostoma 
 c d, is in places and is here cut through. From the end of the tail, 
 at e, a thin rough line runs inwards, nearly to the large spot at /, 
 and is obscurity indicated thence to the end of the hypostoma 
 at c. The spot /' appears to be organic. It is of an ovate form, 
 and has four or five obscure ribs across it at right angles to its 
 greater diameter There are other dark spots scattered irregularly 
 throughout the matrix, that possibly may represent organic struc- 
 tures. 
 
 It is possible that the line e fe may represent the edge of the 
 ventral integument cut through ; for in a rolled-up trilobite this 
 must be exactly its po.sition. The small ov.ate bodies I beli ? to 
 be the eggs. 
 
480 
 
 I'UOCTIKDINOS OF THE OEOLOOICAL SOCIETY. 
 
 Fig. 
 
 EXPLANATION OF PLATES XXXI. A XXXll, 
 Plate XXXI. 
 
 P^ig. J. AHiij)//i(fi pliifi/n-phaliis. StokoH. — I'lidersido, showing tlii> logs; « /'• 
 Huhirn (lirotigh tho rloublurc ; f, ( . oaTitit's on cnfli side of tlic livpostonia ; 
 (/, (/. tuberclos on tlio pygidiuni ; //. (K.']>liHlic doubluro ; /, /, tin.' two IoIwm 
 of the hyj)08toina , m, position of t-he in(nith ; 7^ n, », », joints in tht- legs 
 2 Transverse ideal .'^eetion through tlie thorax ; a. h. tlie doublure of tho 
 pleune ; />, position of tlie Paiulerian organ. The dotted lino from h to h 
 indicates tlie (contour of ili«' ventral surface. 
 
 Fig. 3. Ideal section ihrough tlie head, cutting olT the points of the hypustonia, 
 /, I, ill a plane pnssing through tho eyes ; 1, 2, position of the 1st and lind 
 pairs of legs. 
 
 Fig. 4. .Section through tho tail of a srtiall specimen, showiig (lie doublure, //. 
 
 Fig. 6. Three ))lenne restored, showing the po'<ition of the Pandenan organ at 
 p ; r/, '), portion of the plourie removed 
 
 Pig. G. Supposed leg of Trilobiti^, ligured by Eicliwald : (/, natural size ; i, 
 enlarged. 
 
 Plate XXXn, 
 
 Fig. 1. Asaphus pla'i/oephahis. — Side view of the specimen which shows the 
 legs, somewhat restoi-ed. The dotted line, (/ c^, represents the position of 
 the piano of the Tentral surface nearly. 
 
 Fig. '2. I^orsal view of tlm same; the dotted lines indicate tho position of the 
 hypostoma and legs. 
 
 Fig. ,'5. Cal^iiune. scnarin. — Section through the axis of the thorax: (/, junc- 
 tion of hi»ad and tail ; h, back of the head ; r d, hypostoma ; e, end of the 
 tail ; /, a body showing strui/ture. 
 
 Fig. 4. A group of the small bodies in lig. 'i, enlarged S diameters. 
 
 Fig. b. The organic body seen at / in fig. 4, enlarged li diameters. 
 
 DjSf.T'SSION. 
 
 Mr. WooDWABi) had carefully exarnined Mr. Billings's specimen, 
 and agreed with him in considering that there wa.s nndotibtod 
 evidence of tho presence of ■walking-;ippend;ige(» nndor the thorax. 
 The presence of such limhs might a j>riori have been expected; and 
 the nature of the test anggcfsted that the Trilobites were Avalking 
 rather than swimming forms of Isopods. I'he brauchite had pro- 
 biihly been under the telson ; and thi.si woidd account for its larg(.> de- 
 velo])ment. li was not more surprising to find highly orgauizcd 
 Trilobites than it was to find such highly organized crustaceans as 
 Pferiif^otiis, Eariipieritf^ and SUinoniri in the same beds. 
 
 Prof. Rii'Kin' Jom:s, l'riniij)al D.vwson, and Sir Wm. liOOAN 
 made some remarks, more especially on J'rotichiiites and Cliriiactich- 
 nitos — tho latter having been explained as galleries of Trilobites, by 
 Prof. Jones, when first (exhibited in England. 
 
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