52 E. Billings on the Genus Athyris. 
work was confined altogether to the Carboniferous fossils, among 
which it does not occur. But he did so afterward when he de- 
scribed Professor Sedgwick’s Silurian fossils, as will be shown 
farther on. He was wrong in supposing that all the species 
were imperforate, a matter of little consequence, as it was sim- 
ply an error of observation which does not vitiate. Had the 
genus turned out to be not capable of subdivision, all that could 
done now with this error would be to strike it out. There 
was sufficient in his diagnosis to indicate what group of fossils 
was intended. He was also wrong in supposing SS. concentrica to 
be a Carboniferous fossil: it is Devonian. It may be that he 
mistook some other species with an imperforate beak for that. 
It will be seen farther on that Prof. King made a similar mis- 
take with respect to this very species, having taken T. scalprum 
Barrande, for it; an error which was detected by Mr. Davidson. 
Altogether, he referred eleven species to the genus, several of — 
which have been shown to s 
7. 
simply as a substitute for Athyris, on the ground that this lat- 
ter name implies the absence of a foramen, and is, therefore, 
appropriate for species with a perforated beak. It is quite 
iv, page 357, he says: “This division has already two generi¢ 
names which we cannot preserve, because they are in complete 
contradiction with zoological characters.” The two genera re- 
fe to were Athyris and Actinoconchus. 
fer specially selected 7: concentrica* for the type of his genus, 
an 
s 
ection. He refers to his ‘‘ Prodrome’ 
pen te 
