THE DEVONIAN FOSSILS OF CANADA WEST. 141 
mesial septum in the dorsal valve, (type S. concentrica,) and Athyris 
for those of which 4. tumida is the typical form. This is the most 
just arrangement of the difficulty that has yet been proposed, and has 
been adopted: by F. Reemer in the last edition of Bronn’s “ Letheea 
Geognostica.” 
Mr. Woodward in the “ Manual of the Mollusca,’ adopts Athyris 
in the wide sense as intended by McCoy, but admits Merista as a 
sub-genus for those with a shoe-lifter process. 
In the New York Reports, the species of this genus, until within 
the last four or five years, have been placed in the genus Atrypa. 
In the tenth annual report of the Regents of the University of the 
State of New York, published in 1857, Professor Hall describes six 
species from the Upper Silurian rocks, under the genus Merista, and 
one from the Hamilton group, under Spirigera. This latter, which 
he calls Spirigera spiriferoides, is considered by many authors to be 
identical with S. concentrica. 
In the Geology of Iowa, dated 1858, he describes three species 
from the carboniferous rocks of the Western States, under Athyris. 
These appear to be perfectly congeneric with S. concentrica, or, 
S. spiriferoides as he calls it. 
In the twelfth Annual Report of the Regents, dated 15th March, 
1859, published October, 1859, he proposes a new generic name 
(Camarium,) for those with a shoe-lifter process. This genus is 
identical with Merista. 
In the thirteenth Annual Report of the Regents, published January 
1861, Professor Hall abandons his genus Camarium, finding it to be 
identical with Merista, and then for those shells which have Athyris 
tumida for the type he proposes a new name, Meristel/a. 
Some of the European authors, such as Pictet and Sandberger, 
retain Spirigera, and in his recent highly instructive papers in the 
* Geologist,” Mr. Davidson places all the species under Athyris, but 
says that sub-genera may be admitted provided they be founded on 
good and sufficient distinctive characters. 
It is not necessary to extend this list of references to the opinions 
of palzeontologists. Sufficient appears in the above to shew that the 
nomenclature of this genus is in a state of confusion. I think the 
best way of getting out of the difficulty, is to fall back upon the 
arrangement proposed by Mr. Davidson in his Introduction. 
1. McCoy’s several definitions should be construed literally or 
