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. 



