38 Remarks on the Trilohiie. 



Dr. Dekay ; and if Mr. Stokes's drawing and Dr. Dekay's figure 

 be accurate representations of nature, Ave think they must be 

 drawn from analogous fragments belonging to animals at least 

 specifically distinct. 



Wa 



D 



der surface with lunate processes, somewhat resembling the one 

 just described j but instead of being composed of a flat plate or 

 surface, it forms one that is convex, very much resembling the 

 figure given by Dr. Buckland from Mr. Stokes. From this frag- 

 ment it is perfectly evident, that this lunate structure is composed 

 of an upper and under plate, the one convex and the other plain 

 or fiatj so as to form^ when unitedj a plano-concave, hollow, lu- 

 nate box or cavity. The physiological relations of this struc- 

 ture I am unable to suggest ; but since the above remarks were 

 penned, I have seen a copy of Murchison^s Silurian Systeriij 

 &:c., from which the following extract is made, which may throw 

 some light on this matter, and is otherwise interesting. ^'1 have 

 seen the work of Pander at too late a period to enable me to pro- 

 fit much by his views concerning the original structure of the 

 trilobite or the adaptations of the tegumentary skeleton of the an- 

 imal to its habits, into the consideration of which he enters at 

 length. He certainly throws some new light on the nature of 

 these creatures by exposing the interior or under surface — partic- 

 ularly that of their heads, in which he points out several divis- 

 ions, and considers them to be the thoracic plate and jaws. The 

 central portion, or that which was formerly described by Mr- 

 Stokes from a North American specimen, he considers to have 

 heen connected with the head by cartalage only, and to have 

 served as a thoracic plate to protect the stomach, the form of which 

 varies in the different genera of trilobites found in Russia. On 

 referring this subject to my friend Mr. W. Mc Lay, whose knowl- 

 edge of invertebrated animals is so profound ; he assures me that 

 this plate on the under side of the head, above alluded to, must be 

 considered as the lahrum or upper lip. The trilobite is thus 

 brought into close analogy with certain entomostracha such as 

 the Aprs Cancriformis, &c," 



We 



the 



present remarks respecting the organization of the under surface 

 of the trilobite, calymene bufo, a name which we proposed some 

 years since in our little work on these interesting reliques. Other 



