CARBONIFEROUS SPECIES. 83 



projection, fitting into a coiTesponding sinuosity in the front of the other 



valve, just as we see in A. Roissyi; but the sinus in all of them becomes a 



narrow, very shallow sulcus, at a short distance from the front, instead of 



being broadly rounded or somewhat flattened, as we usually see in large 



examples of I'Eveill^'s species. 



Locality and position. — :From the light-colored Carboniferous limestones 



of Ruby Group ; also, from same in Wachoe Mountains ; Mahogany Peak ; 



Egan Range, Nevada. 



Athyrts subtilita. Hall. 



Plate 8, figs, 6, 6 a. 



Spirifer Boissyi, d'Orbigny (1843), Yoy. dans Am(5r. Merid., 46, pi. iii, figs. 17 and 19, 



(by error marked Terehratula Peruviana on the plate ; not Athyris Boissyi, 



I'Eveille, sp.). 

 Terehratula subtilita, Hall (1852), Stansbury's Report Salt Lake Exp., 409, pi. 4, figs. 1 



and 2 ; and again (1858) in Iowa Geol. Report, I, part ii, 714. — Marcou (1858), 



Geol. N. Am., 52, pi. vi, figs. 9 a, 6, c, d, e,f. 

 Athyris differentis, McChesney (1860), Descriptions New Palseozoic Fossils, 47. 

 Athyris subtilita, Davidson (1861), Brit. Carb. Brach., 86, pi. i, figs. 21-22, and pi. 



xvii, figs. 8-10.— Salter (1861), Quart. Jour. Geol. Soc, XVII, pi. iv, figs. 4ffl, &.— 



Meek (1876), in Col. Simpson's Report Expl. across the Great Basin of Utah, 



350, pi. 2, figs. 4 «, 6. 

 Compare Terehratula argentea, Shephard (1838), Am. Jour. Sci. and Arts, XXXLV, 152, 



fig. 8; also, Athyris subquadrata, Hall (L858), Iowa Report, I, part ii, 703, 



pi. 27, figs. 2 a, h, c, d. 



Of this very common species, there are in the collection from several 

 localities in Nevada well-marked and characteristic examples, agreeing in 

 all respects with those found in the Coal-Measures of the Mississippi Valley, 

 from Kansas and Nebraska to Texas, as well as westward to New Mexico, 

 and eastward to Ohio. If Athyris subquadrata, Hall, is really identical with 

 this species, which it certainly very closely resembles, then it must be com- 

 mon both to the Upper and Lower Carboniferous in the West ; but if that 

 is a. distinct species, A. subtilita would seem to be confined, so far as known, 

 to the Coal-Measures in the Mississippi Valley ; though the English speci- 

 mens referred to A. subtilita by Mr. Davidson came from" the Lower Car- 

 boniferous. 



Mr. Salter identified with this species a South American shell from the 

 Andes, and also a form described from there by d'Orbigny, and referred by 

 him to Athyris Roissyi: and, from the figures given by these authors, as well 



