NUCLEOSPIRA OF THE HAMILTON GROUP. 
381 
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 Falls of the Ohio; and in the Hamilton group, in the 
vicinity 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. Williams, collected in the Hamilton group of Hardy county, Ya.; and 
it likewise occurs near Cumberland, Maryland. 
Note. In the arrangement of the preceding genera of the Family Spibifebiile, 
I have followed what appeared to be the most natural order ; and since we pass 
almost insensibly from Spieifeba to Spibifebina and Cyetina, it is scarcely pos¬ 
sible, from what we know, to remove the Genus Tbematospiba from the relation 
in which I have placed it. The Genus or Subgenus Rhyxchospiea 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 Nucleospiba, which may, 
perhaps, be more nearly related to the following than to the preceding genera. 
So far as we 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 Athyeis, Meeista and Mebistella, will be 
farther removed from Spieifeba 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 Athyeis, 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 Mebistella are very nearly like those of Spieifeba 
proper, while those of Athyeis show a wide departure in the character of the 
loop and intercalated lamellae. Regarding the Genus Mebistella in all its charac¬ 
ters as now determined, I w T ould place it before Athyeis in its relation to 
Spieifeba. 
Paleontology IV.] 
36 
