234: Mr. EK. Billings on the Genus Athyris. 
objected to by several distinguished paleontologists, and in con- 
sequence thereof abandoned by its author, yet I believe that, on 
a careful examination of all the circumstances, it will be found 
to be perfectly just toward the parties concerned, and in no re- 
spect inconsistent with the rules of zoological nomenclature. It 
was the first subdivision of the genus published, and should 
therefore take precedence over all others. 
Previously to 1853 Athyris was only known as a single large 
genus of Brachiopoda, which included such forms as Terebratula 
concentrica, Von Buch, T. tumida, Dalman, and 7. Herculea, 
Barrande. In that year Mr. Davidson divided it imto two 
smaller genera, confining the name Athyris to that section for 
which it was most appropriate, with tumida or Herculea for the 
type, and adopting Spirigera, D’Orbigny, for the other type, 7. 
concentrica. It was afterwards found that Athyris, as then re- 
defined, included two genera; and in consequence it has been 
again divided by separating all those typified by 7. Herculea 
under the name of Merista, a genus proposed but not clearly 
characterized by Prof. Suess in 1851. This is the classification. 
which I believe to be the true one. While discussing it I shall, 
throughout this paper, when I may have occasion to refer to the 
species above named, designate them Athyris tumida, Spirigera 
concentrica, and Merista Herculea. 
Those who are opposed to this arrangement contend that, as 
all the species which M‘Coy placed in the genus at the time he 
first described it belong to the group typified by S. concentrica, 
the name Athyris must be retained for that group, and cannot 
now be transferred to the other section of which A. tumida is 
the type. This reasoning, according to my views, can only hold 
good in case it be first proved that M‘Coy specially confined the 
genus to species having the generic characters of those in his 
original list, or pointed out one of them as the type, or drew up 
his diagnosis in such a manner as to exclude A. tumida. In 
this paper I shall endeavour to show— 
1. That M‘Coy did not limit his genus to the species first 
placed in it. 
2. That, on the contrary, he and other naturalists understood 
it to include both A. tumida and S. concentrica. 7 
3. That, according to the laws of zoological nomenclature, the 
subdivision made by Davidson in 18538 cannot be set aside. 
4, That Davidson’s classification has been adopted in several 
works, some of them of great influence and wide circulation. 
In order to prove the above propositions, I shall give the 
more important facts of the history of the genus, with M‘Coy’s 
original figure, and shall quote some of the laws above mentioned 
in full. Much of this, of course, belongs to the common stock 
Se ay PE 
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