TRENTON LIMESTONE. 241 
I have examined fragments of a similar species in the collection of Mr. Carry of Cin- 
cinnati; but the fimbrize beneath the maxille in that one are longer and fewer in number, 
which I conceive to be a specific distinction. In that species, the central posterior spine of 
the buckler is very long, extending half the length of the thorax. 
A comparison of our species with the one figured and described by Dr. Locke ( cited 
above ), shows several points of resemblance. The fimbrie beneath the maxille are the 
same in number; but the representation of the cephalic shield, particularly the glabella, 
is quite different, as also the nodes or tubercles upon the segments of the thorax. These 
differences are clearly distinguishable on a comparison of the figures. The species of 
Locke is undoubtedly an Acidaspis, and not a Ceraurus, which differs in many essential 
characters. 
Fig. 4 a. Front view of the specimen, which is folded (natural size). 
Fig. 4 6, The same enlarged, to show more distinctly this part of the fossil. 
Fig. 4 c. Dorsal view (natural size). d. The same enlarged. 
Fig. 4 e. The caudal extremity and part of the thorax enlarged. 
Fig. 4 f. Margin of the maxille enlarged, showing the fimbriz. 
Position and locality. I have received this specimen from Mr. Locan, the Geologist of 
Canada, who obtained it, with the Calymene senaria and other Trenton limestone fossils, 
at the Bay of Quinta on Lake Ontario. 
300. 2. ACIDASPIS SPINIGER (n. sp.). 
Pu. LXIV. Fig. 5. 
Glabella oval, margined laterally by a deep broad groove, front nearly straight, pos- 
teriorly extended into a strong spine ; surface tuberculated. 
This fragment is all that I have seen of this species within the State of New-York : 
another similar one, with a spine an inch in length, has been obtained by Mr. Loean near 
Montreal. The western species alluded to, bears some analogy to this one. 
I have referred this fragment to the Genus Acrpaspis, from the long posterior spine of 
the glabella, which is known to me as occurring only in this genus and Trinuceus. 
The tuberculated surface is likewise peculiar, and different from that of other genera in 
the lower strata. 
Position and locality. In the central part of the Trenton limestone in the Mohawk valley, 
and in a similar position near Montreal. 
| PaLZonToLoGY.] 31 
