TRILOBITES. 



419 



THE TRILOBITES. 



Near the Limuli and other Entomostraca provided with a great number of legs, 

 should be arranged, in the opinion of M. Alexandre Brongniart, and other natu- 

 ralists*, those singular fossil animals, at first confounded together under the common 

 denomination of Entomolithus paradoxus, but now called Trilobites, of which that 

 author has published an excellent monograph, illustrated by good lithographic figures. 

 According to this hypothesis, we must admit, as a positive fact, or at least as most 

 probable, the existence of locomotive organs, although, notwithstanding all research, 

 no vestige of them has yet been detected.! Supposing, on the other hand, these fossil 

 animals to be destitute of such organs, I have supposed that they are more naturally 

 allied to the Oscabrions, or rather that they formed the primitive type (la souche 

 primitive) of the articulated animals, being allied, on the one hand, to the last- 

 mentioned Mollusca, and on the other, to the above-mentioned Crustacea, as well 

 as to Glomeris J, to which certain Trilobites, such as Calymene, make an approach 

 as well as to the Oscabrions, because, like them, they are capable of contracting them- 

 selves into a ball. Since the publication of the work of M. Brongniart, several natu- 

 ralists have not agreed with his opinion, but, on the other hand, have either partially 

 or entirely adopted mine : others still hesitate. Be this as it may, these animals 

 appear to have been annihilated during the ancient revolutions of our planet. 



With the exception of the heteromorphous genus, Agnostus, the Trilobites have, like 

 the Limuli, a large anterior segment, in the form of a shield, nearly semicircular, or 

 lunulated, and succeeded by about twelve to twenty-two Begment8§, all, except 

 the last, being transverse, and divided by two longitudinal furrows into three rows of 

 lobes, whence the origin of the name of Trilobites. 

 author- llulomostracites. 



They are named by some 



The genus Agnottut, Brong., is the only one which has the body cither semicircular or kidney-shaped. In 

 all the other penera it ^ oval or elliptic. 



Calymene, Brong., differs from the others by the power it possessed of contractual? the 1 ody Into ■ hall, in the 

 same manner as Spheeroma, Armadillo, Glomerit, that is, by causing the two extremities to appr o xi m ate beneath 

 the breast. The shield, as broad or broader than long, exhibits, as in Ataphut and Ogygia, i"" eye likeemini i 

 The segments do not extend laterally beyond the body, and arc united together as far as the extremitj ; the body 

 is terminated posteriorly in a kind of triangular, elongated tail. 



• M. K Dealongchamps, Professor at tin- I of Caen, the 



nutit, M. Dalinnii, unci others, have recently pub- 



fossils. U. V. Audoulu, having 



adopted tl pinli I Hi ed, in s memoir up 



t, that whleh I bad given, whereby I bad approximated tl 



est essential difficulty was to prow the ex- 

 istence of legs, and I failed Id dolus;. As to the application 

 nf bis I rrilobitei, it eppi 



>iuK at the se 

 r ■ the abdomen ol insects alone represent the 



thoi tx of i d Crustacea. 



t Mr [ Parkinson 



.11 ... and thai they arc ongnicn- 



- . ■ ■'■■ '.• "inhittft /■ rw/oo., 



iiunlri Jr-t Science! \ iiur* iln.) 

 emit, ton now n Brani 



. ebareetti 

 . ■ , and Armadliln ; aud i 



, which la at tho head of Its 

 11 and the ti 

 Idently approaches, in rc»[»rct to th 

 : . Iiul l*. 



doc. rot spi > mth lateral 



mi from 



■ im, tiul vrhlch approximates thcra to Armadillo, and cspcclsllr 

 to Tyloa. The r *».'<! baacoe 



nt ttmt they had, like the LlmoJ one, of 



which the eoi ; want 



of superior anl th Umulue. 



$ It appears thai in vftr i partlcularij In Asaphne, 



tin- In' addition t-> tl 



. A from each .it lit r nt the sldee, and nt enotl eg the 



post*abdomen or tali, tngnlar dr semiinnar form, eahi 



Istons, which do doi eol the sldee. In P 

 • >u the i Q tted or urn' 



tlons, quite distinct, and ol which tweni 



mentioned tir Connl tl 

 Afar., June, 1 11), which he considers ihoul 



I BUttS, inn 



I'k' point,. I 

 of long flattened ptatea, witbont artlcnl 

 and folded Im-k ,in the nld i*l itate, at 



. t.i tlic Uirri. i»M« h 



i. all dee. 



I The Squill*?, v i t Sili) 



: ilinr segments dli Idt d Into I 



, tu-i. but llic.r lllici at Mid do 



not form deep channels. 





