NUCLEOSPIRA OF THE HAMILTON GROUP. 281 



Geological formation and localities. This species is known in the Schoharie 

 grit, in Albany and Schoharie counties; in the Corniferous limestone at Lapham's 

 mill in Ontario county, at Caledonia in Livingston county, and at Williamsville in 

 Erie county, New- York, and J'alls of the Ohio; and in the Hamilton group, in the 

 vicinit}' of Apulia in Onondaga county, shores of Seneca and Cayuga lakes, Canan- 

 daigua lake, Geneseo, York, Moscow, Pavilion, Alexander, Darien, Hamburgh, 

 Eighteen-mile creek, and other localities in the western part of the State of New- 

 York. 



I have received very fine specimens of the internal casts of this species from 

 Dr. G. A. WiLLi^iMS, collected in the Hamilton group of Hardy county, Va.; and 

 it likewise occurs near Cumberland, Maryland. 



Note. In the arrangement of the preceding genera of the Family SpiRrFERiD^, 

 I have followed what appeared to be the most natural order ; and since we pass 

 almost insensibly from Spirifera to Spiriferina and Cyrtixa, it is scarcely pos- 

 sible, from what we know, to remove the Genus Trejiatospira from the relation 

 in which I have placed it. The Genus or Subgenus Ehynchospira will therefore 

 follow, and all those forms referred to the Genus Retzia will come into the same 

 relation. I have placed in this association the Genus Nucleospira, which may, 

 perhaps, be move nearly related to the following than to the preceding genera. 

 So far as wc know, the structure of the spire ( though with some variations ) is 

 similar in all these, and the presence of an area or false area may be recognized 

 in all or nearly all of them. 



By this arrangement the Genera Atiivris, Merista and Meeistella, will be 

 farther removed from Spirifera proper, while it might appear that their relation 

 would be more nearly with the smooth Spirifers. I have followed this order of 

 arrangement, beginning with the Genus Atiiyris, because I had so arranged the 

 matter and the plates of the volume before having made the final studies of the 

 interior and the determination of the structure of the spires. It will be seen, 

 however, that the spires in Meristella are very nearly like those of Spirifera 

 proper, while those of Atiiyris show a ■vYi<Je departure in the character of the 

 loop and intercalated lamelhe. Regarding the Genus Meristella in all its charac- 

 ters as now determined, I would place it before Athyris in its relation to 

 Spieifera. 



PaljEontoloot IV.] 86 



