Mr. E. Billings on the Genus Athyris. 239 
dans ce petit mémoire qui n’est pour ainsi dire qu’un résumé d’un 
plus grand travail que je publie en ce moment dans le London 
Geological Journal.” 
Upon the above I shall only remark that it is quite clear 
that Mr. Davidson then regarded S. concentrica and A. tumida as 
congeneric, and that whatever new genus might be established 
it would include both species. 
In 1852, M‘Coy, in the second fasciculus of the ‘ British 
Paleozoic Fossils,’ page 196, redefined Athyris as follows :— 
*« Gen. Char.—Nearly orbicular or ovate, both valves convex ; no 
cardinal area, foramen, or hinge-line; spiral appendages to beak of 
entering valve very large, nearly filling the shell; a strong mesial 
septum in the rostral part of entering valve ; dental lamellee mode- 
-rate; tissue of shell apparently fibrous. 
*«Qne specimen [of 4. tumida] shows the pallial and ovarian im- 
pressions to be thick, numerous, and dichotomizing frequently from 
beak to margin.” 
In the work cited and in the third fasciculus we find the fol- 
lowing species :—A. fumida, S. concentrica, ambigua, De Roissy, 
expansa, globistriata, globularis, gregaria, paradoxa, pectinifera, 
and squamigera. This shows clearly enough his views of the 
extent of the genus—that is to say, that, as it was then under- 
stood, it included both A. tumida and A. concentrica. In com- 
menting on this, Prof. Hall says :—“ The fact that M‘Coy cited 
this as an Athyris no more renders it an Athyris than it was 
made Atrypa by being thus described by Dalman; and it was 
just as free for the foundation of a genus after the citation of 
M‘Coy as before”*. This is true enough in part. It was free 
for the foundation of a genus until 1853, when Davidson used 
it for that purpose; but since 1853 it has never been free. 
The above is quite sufficient to prove my first and second 
propositions. 
I am not aware of anything else of much importance, with 
the exception of what relates to Merista, having been published 
_ up to 1853, when Davidson’s excellent work, the ‘ Introduction 
to the Classification of the Brachiopoda,’ made its appearance, 
in which the genus was first subdivided. But, before entering 
upon this, I shall notice the remarks of Prof. Suess on the genus 
Merista. 
This genus was proposed by Prof. Suess in 1851; but he did 
not then sufficiently characterize it. The following is all that I 
can find relating to it that was published previously to 1853 :—- 
_ “Mr. E. Suess communicated the results of the investigations on 
several Brachiopods, from the Bohemian transition rocks, which had 
* Silliman’s Journal, ser. 2. vol. xxxii. p. 131. 
