CARBONIFEROUS SPECIES. 83 



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

 valve, just as we see in A. lioissyi; 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'Eveille's species. 



Locality and position. — From the liglit-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. 

 ISjnrifer Boissyi, d'Orbigny (1843), Voy. dans Amer. Merid., 46, pi. iii, figs. 17 aud 19, 



(by error marked Terehratula Peruviana on the plate; uot Athyris Boissyi, 



I'Eveille, sp.). 

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



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



Geol. N. Am., 52, pi. vi, figs. 9«, h, c, d, e,/. 

 Athyris diferentis, McUhesuey (1800), Descriptions New PaUTOzoic Fossils, 47. 

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



.\vii;figs.8-10.— Salter (1861), Quart. Jour. Geol. Soc, XVII, pi. iv, figs, ia, b.— 



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



350, pi. 2, figs. 4 a, b. 

 Compare Terehratula argeritea, Shephard (183S), Am. Jour. Sci. and Arts, XXXIV, 152, 



fig. 8; also, Athyris subquadrata. Hall (1858), Iowa Report, I, part ii, 703, 



pi. 27, figs. 2 a, b, 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- 

 raon 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 refen-ed 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 Boissyi: and, from the figures given by these authors, as well 



1 



