tRENTON LIMESTONE. 



241 



I have examined fragments of a similar species in the collection of Mr. Carly of Cin- 

 cinnati ; but tlie finil)riae beneath the maxilla; in tiiat one are longer and fewer in number, 

 which I conceive to be a specific distinclion. 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 fanbritc beneath the maxilla; are the 

 same in number; but the rc])resentalion of the C(;phalic shield, particularly the glabella, 

 is (|uite different, as also the nodes or tuljercles 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 b. 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/ Margin of the maxilloe enlarged, showing the fimbrise. 



Position and locality. I have received this specimen from Mr. Logan, 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. s/).). 



Pl. 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. Logan near 

 Montreal. The western species alluded to, bears some analogy to this one. 



I have referred this fragment to the Genus Acidaspis, from the long posterior spine of 

 the glabella, which is known to me as occurring only in this genus and Trinucleus. 

 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. 



[Paleontology.] 



31 



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