Mr. E. Billings on the Genus Athyris. 239 



dans ce petit memoire qui u'est pour ainsi dire qu'un resume d'ua 

 plus grand travail que je publie en ce moment dans le London 

 Geological Journal." 



Upon the above I shall only remark tliat 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 1853, M'^Coy, in the second fasciculus of the 'British 

 Palaeozoic 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 lamellae mode- 

 rate ; tissue of shell apparently fibrous. 



" One specimen [of A. 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. tumida, S. concentrica, amhigua, De Roissyi, 

 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 



* Silliinan's Journal, ser. 2. vol. xxxii. p. 131. 



