Mr. E. Billings on the Genus Athyris. 245 



A. pseudo-scalprum {Terebratala pseudo-scaljjrum, Barrande), A. 

 scalprum [Terebratula scalprum, Fried, Roemer)" {op. cit. p. 331). 



They also recognized >S'. concentrica as the type of Sjnrigera. 

 "Die typische Art hi Sp. concentrica {Terebratula concentrica, 

 Bronn). Andere Arten sind Sp. pectimfera {Atrypa pectinifera, 

 Sowerby), aus dem Zeclistein, Sp. Roissyi {Sp. de Roissyi, Le- 

 veille)/' &c. {op. cit. p. 332). 



In the same year Eichwald placed A. tumida in Athyris, and 

 S. concentrica in Spirigera^'. 



In 1860 he also introduced the same classification in his great 

 work on the Palaeontology of Russia. The Russian species are 

 A. tumida, didyjna, ungula, cassidea, S. concentrica and ambiguaf. 



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 MoUusca^ (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 Athyris, 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 palaeontologists 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 Athyris 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. 



t Lethfea Rossica, vol. ii. p. 731 {Athyris), p. 735 (Spirigera). 



X In this work Mr. Woodward separates Merista (although with doubt) 

 as a subgenus, and refers A. tumida to Athyris. 



