E. Billings on the Genus Athyris. 53 
S. Ceres, vultur, Circe, passer, Herculea, harpya, Hecate, tumida, con- 
J ia, Ferronesensis, Ez 
pay mpomanensis, 
Mayendorfi, Roissyi, serpentina, lamellosa, ambigua, Blodena, plano- 
sulcata, expansa, pentaédra, A Tague trigonella, quinquecostata, quad- 
ricostata, tricostata and cristigall 
Several of the above species do not belong to the group. Th 
list shows that D’Orbigny regarded the genus as including ial 
only the types of Athyris and Spirigera but also that of the genus 
Merista (M. Herculea) which I shall notice farther on.» F think 
it quite certain that had D'Orbigny been aware that the genus 
was capable of subdivision, he would have retained Ath for 
one of the groups which have the beak imperforate. Indeed, 
according to the laws of nomenclature, he could not have done 
_ with any probability of producing a permanen nt classi- 
catio 
In a valuable paper, read before the Geological Society of 
France, in May, 1848, on the Brachiopoda of the Upper Silurian 
rocks of England,* Mr. Davidson made the following observa- 
tions on D’Orbigny’s genus: 
Vient ensuite le genre Spirigera que le méme auteur établit pour les 
oot ly we iti des spires internes placeés de la méme maniére 
wera, ambigua, Helmerseni, imate ” Cam, mpomanensis, Ferrone. 
Ezquerra, Hispanica, ont déja été distinguées par M. de Verneuil comme 
devant former une section & art, qu'il a igh e la section des | fuse 
frie. Je suis de lopinion de hg d’Orbigny qu’el nt 
genre. peice minutieuse q e M. Bouchard a "hin de la Torelretule 
n laisse aise doute; mais ce genre n’ayant pas en- 
core été ebtiveriableniéat caractérisé, je m ’abstiendrai de l’adopter dans 
ce petit mémoire qui n’est pour oe dire qu’un résumé d’un plus grand 
travail que je publie en ce moment dans le London Geological Journal. 
oe the — I shall only remark that it is quite clear 
that Mr. Davidson then regarded SS. concentrica an tumida as 
congeneric; and that whatever new genus might be catabhichadly 
it would include both s species 
Tn 1852, Mater) in the 2nd Fasciculus of the “British Paleo- 
Zoic Fossils, ” nage 196, re-defined Athyris as follows:— 
“ Gen. Ch.—Nearly orbicular or ovate, both valves convex; no cardi- 
nal area, foramen, or on St spiral appendages to beak of en —<- 
li 
valve very large, nearly filling the shell; a strong mesial septum in 
rostral part of entaring valve dental lamelle moderate ; tissue of shell 
apparently fibrous. 
Mémoire les Brachiopodes du Systime silurien ssrn mpi € Ags 
M. Th Devons, ell Genk toe Pr pp. 900, 318 
