82 PALEONTOLOGY. 



see in Bhynchonella ; but some scars of the adductor muscles seen near the 

 middle of the valve seem to be more like those of Athyris. If a Bhyncho- 

 nella, it would, of course, belong- to the section of the genus including 

 R. acuminata. 



Locality and position. — Light-colored Carboniferous limestone of White 

 Pine Mountains, Nevada. 



Athyris Koissyi, l'Eveill6 (sp.). 



Plato 9, figs. 3, 3 a, 3 ft. 

 Spirifvr dc Roissyi, l'Evcill6 (1835), M^ui. Soc. G6ol. France, II, 39, pi. ii, figs. 18-20. 

 Spir'i/rr iiMnistriatus, Phillips (183G), Geol. Yorks., II, 220, pi. x, fig. 19. 

 Sph-i/n-Jimhriatus, Phillips, ib., 220. 

 Icrcbrattila Koissyi, De Verneuil (1840), Bull. Soc. G6ol. Frauce, XI, 2.59, pi. iii, figs. 



lh,c,d (not 1 a and e).— De Koninck (1843), Au. Foss. Carb. Belg., 300, pi. 



xxi, fig. 1 (not pi. XX, fig. 1). 

 Athyris depressa, ]\IcCoy (1844), Syuop. Carb. Foss. Ireland, 147, pi. xviii, fig. 7. 

 Athyris de Roissyi, McCoy (1855), Brit. Pal. Foss., 433. 

 Athyris glahristriata, McCoy, ib., 434. 

 Athyris Roxjssi, DiWxCinow (ISGO), Monogr. Carb. Brach. Scotland, 16, pi. i, fig. 12; 



and (1861) Brit. Carb. Brach., 84, pi. xviii, figs- 1-11. 

 ? Athyris suhlameUosa, Hall (1858), Iowa Report, II, part 2, 702, pi. xxvii, figs.l a, b, e. 



There are among the collections before me a number of specimens, 

 some of which agree very closely with A. Roissyi in form, size, and general 

 appearance ; but, as none of them show the fringed lamellae of growth so 

 characteristic of I'Eveille's species, it is with considei'able doubt that I have 

 identified them with that widely-distributed Carboniferous form. Still, as 

 the peculiar surface-mai-kings are said not to be always preserved in speci- 

 mens of A. Roissyi, it is quite possible that they may have originally existed 

 in our specimens, which came from a limestone matrix. They all show 

 rather distinct, subinibricating marks of growth, but without traces of 

 projecting fimbriated lamellte. Some of the larger specimens have exactly 

 the transversely-oval form and well-defined mesial sinus seen in mature, 

 wide individuals of A. Roissyi; while other smaller individuals are propor- 

 tionally narrower, with a much more prominent beak, and more rapidly- 

 sloping posterior lateral margins, thus passing by easy gradations into forms 

 that it is difficult to separate from A. suhtilita, Hall, especially in specimens 

 that have the surface-markings not well preserved. The adult specimens 

 all show the sinus of the ventral valve terminating in a rounded marginal 



