38 Remarks on the Trilobite. 
Dr. Dekay ; and if Mr. Stokes’s drawing and Dr. Dekay’s figure 
be accurate representations of nature, we think they must be 
drawn from analogous fragments belonging to animals at least 
specifically distinct. 
In Mr. Wagner’s cabinent there is another fragment of the un- 
der surface with lunate processes, somewhat resembling the one 
just described ; 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 flat, so as to form, when united, a plano-concave, hollow, lu- 
nate box or cavity. The physiological relations of this struc- 
ture [ am unable to suggest; but since the above remarks were 
penned, I have seen a copy of Murchison’s Silurian System, 
&c., from which the following extract is made, which may throw 
some light on this matter, and is otherwise interesting. “I 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 
been 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 dabrum or upper lip. The trilobite is thus 
brought into close analogy with certain entomostracha such as 
the Apus Cancrirormis, &c.” 
We have called the fossil remain which has occasioned 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 
—— 
