Mr. £. Billings on the Genus Athyris. 245 
A. pseudo-scalprum (Terebratula pseudo-scalprum, Barrande), A. 
scalprum (Terebratula scalprum, Fried. Roemer)” (op. cit. p. 331). 
They also recognized S. concentrica as the type of Spirigera. 
“Die typische Art ist Sp. concentrica (Terebratula concentrica, 
Bronn). Andere Arten sind Sp. pectinifera (Atrypa pectinifera, 
Sowerby), aus dem Zechstein, Sp. Roissyi (Sp. de Roissyi, Le- 
veillé),”” &c. (op. cit. p. 332). 
In the same year Hichwald placed A. tumida in Athyris, and 
S. concentrica in Spirigera*. | 
In 1860 he also introduced the same classification in his great 
work on the Paleontology of Russia. The Russian species are 
A.tumida, didyma, ungula, cassidea, 8. concentrica and ambiguat. 
In my studies of the Canadian Brachiopoda I had no occasion 
to describe any species of this group until 1859, when I com- 
menced a series of papers on the Devonian Fossils of Canada 
West. At that time I had not fully investigated the subject, but 
understood, from a paper published by Mr. Davidson in the 
‘Geologist’ (vol. i. p. 456), and also from Woodward’s ‘ Manual 
of the Mollusca’ (p. 223), that A. tumida and S. concentrica were 
thought to be inseparable {. Not feeling perfectly satisfied that 
this was the correct classification, I prefaced my descriptions 
with the following remarks :— 
“Genus Aruyris, M‘Coy. 
‘There is much difference of opinion as to the propriety of retain- 
ing this generic name. It implies that the shells have no foramen 
in the ventral valve ; and yet many are placed in the genus which 
have the beak distinctly perforated. Some paleontologists are there- 
fore in favour of using D’Orbigny’s appellation Spirigera instead of 
Athyris. Nearly all of the Silurian species, and some of those from 
the Devonian rocks, have the beak so strongly incurved that no 
foramen can be seen. For such, at least, the name dAthyris does not 
appear to be very inappropriate. Mr. Davidson still retains it, not 
only for those which have the foramen concealed, but also for those 
with it open. It appears probable that the genus will sooner or 
later be subdivided ; and in that case Athyris might be retained for 
the species with closely incurved beak, and Spirigera for some of the 
others. I shall give some account of the generic characters of this 
group of shells in another article. The following species are placed 
in the genus provisionally.” —Canadian Journal, ser. 2. vol. v. p. 273 
(May 1860). 
In that paper I described two species with closed beaks (A. 
* “Beitrag zur geographischen Verbreitung der fossilen Thiere Russ- 
lands,” Bull. Soc. Imp. Nat. Moscou, vol. xxix. pp. 419, 422. 
+ Lethza Rossica, vol. ii. p. 731 (Athyris), p. 735 (Spirigera). 
+ In this work Mr. Woodward separates Merista (although with doubt) 
as a subgenus, and refers A. tumida to Athyris. 
