355 



some si)Ccimens in the collection too imperfect to be fignred, than in the 

 cue from which the figure given on plate 1 was drawn. 



Locality and position. — Carboniferous limestone, at Katlahwoke Creek, 

 just west of tbe i>rincipal range of tbe Rocky Mountains, latitude 49° 

 north, longitude 114° west. 



Genus SPIRIFER, eowerby. 

 Spirifee Keokuk, Hall? 



Plate 1, figs. 3, 3, a. 



Spirifer Keokuk, Plall (1858), Geol. Report Iowa, i, 642, pi. xx, figs. 3, a-cl, aud 2 d. 

 Sj}infer Keokuk, var., ib., 676, pi. xxiv, figs. 4, a, b, c, d. 



The specimens of this Spirifer in tbe collection are very imperfect; 

 but as far as tbeir characters can be made out, they present no peculiar- 

 ities by which tbey can be distinguished from the shell described by 

 Professor Hall under the name 8. Keolnili. Colonel Simpson, Mr. King, 

 and Dr. Hayden have also brought, from dark-bluish and gray lime- 

 stones at various localities in Utah aud other far western districts, 

 specimens of apparently the same shell. There is also in the Coal- 

 Measures of the Western States a Spirifer that has been described by 

 Professor Hall under the name ;S'. opinius, in his Iowa Eeport (aud, as 

 I think, more recently by Professor McChesuey, under the name S. 

 suhventricosus), that seems to be very closely allied. 



Locality and position. — Gray Carboniferous limestone ; Kooteuay 

 rauge of Eocky Mountains. 



Genus ATHYRIS, McCoy, 1844,=zSPIRIGERA, d'Orbigny, 



1847. 



Athyeis subtilita, Hall (sp.). 



Plate 1, figs. 2, 2 a. 



Terebraiula Eoysii, d'Orbiguy (1842), Voy. daus I'Amer. M«?rid., viii, 44, pi. iii, figs. 

 17-19; (not L'Eveill6 (sp.), 1836). 



Terebraiula tubtiiita, Hall (1852), iu Stansbury's Eeport Exp. to Great Salt Lake, 

 409, pi. iv (by error pi. ii), figs. 1, a, b, aud 2, a, b. — Schiel (1855), Eeport Pacific 

 E. E. Survey,' ii, 108, pi. 1, figs. 2, «, &. — Davidson? (1856), Brit. Garb. Bracb., 

 18, pi. 1, figs. 21 aud 22.— Hall (18.56), Eeport Pacific E. E., iii, 101, pi. ii, figs. 

 1 aud 2. — Marcou (1858), Geol. N. Am., 52, pi. vi, fig. 9, o, b, c, d, e,f. 



Athyris subiila, Davidson (1856), British Garb. Bracb., 86, pi. i, figs. 21 aud 22, aud pi. 

 xvii, figs. 8-10. — Salter (1861), Qr. Jour. Geol. Soc. Loud., 64, pi. iv, fig. 4. 



As nearly as can be determined from a single specimen of the shell 

 under consideration, it appears to agree well with A. subtilita in form 

 and general appearance. It is smaller, however, than the usual adult 

 size of that species; but, like other species of the genus, that shell is 

 known to vary considerably iu size at different localities. 



In the ]\Iississippi Valley, A. subtilita is usually regarded as being 

 confined to the Coal-Measures and Permo-Carboniferous beds; but the 

 British examples cited above came from the Lower Carboniferous. We 

 have iu our Lower Carboniferous (Chester group) a form described, by 

 Professor Hall in the Iowa Report, under the name A. sub<iuadrata, which 



