470 CARKONIt'EROUS FOKMATIONS AND FAUNAS OF COLORADO. 



sha})i' oi B. xicrciisiiiiiiis. while tlie growth lines iii'(>. strono'cr luid more regular than 

 in the nmturc form. I am prepared to believe that halt'-gi'<nvn shells of G. gigantem? 

 can not be distinguished from B. ercunfiui, and that young specimens of B. vrmKicx 

 (and probably of tlu^ largi! form also) arc indistinguisha))le from B. uteixmftiamiii. 



As regards the specific relationship of the Coloradt) (and the Illinois) form with 

 Worthen's species, it is evident that an internal cast of the former would have the 

 rounded contour of the latter, and the large size of both lends probability to the 

 identiiication. It need not be pointed out, however, that B. giganteun differs in 

 shape from the form provisionally referred to it, at least in that it is a more rapidly 

 expanding and somewhat more flaring type. The circumstance that Worthen's 

 specimen is an internal cast and perhaps otherwise not well preserved, while the 

 aperture of my own is defective, widens the iield of individual judgment. 



Locality and horlson. Sa,n Juan region (station 2287); middle portion of the 

 Herinosa formation. 



Bellerophon (sensu strictu) percarinatus Conrad? 



1842. Bcllerophon percarinatus. Conrad, Acad. Nat. Sci. Philadelphia, .Tour., (1), vol. 8, p. 268. 



Goal Measures: Inclined plane of the Alleghany Mountain, in l)lack shale overlying the stratum 

 of coal No. 7, Huntingdon, Pa. (?). 

 1855. Bellerophon percarinatus. Norwood and Pratten, Acad. Nat. Sci. Philadelphia, Jour., (2), vol. 3, 

 p. 74, pi. 9, figs. 4a-c. 

 Coal Measures: Grayville, 111.; Posey County, Ind., 5 miles below New Harmony. 

 1872. Bellerophon percarinatus. Meek, U. S. Geol. Surv. Nebraska, p. 227, pi. 11, fig. 14. 



Upper Coal Measures: Nebraska City and Brownville, Nebr. ; Grayville, III. : Illinois, Iowa, 



Missouri. 

 Lower Coal Measures: West Virginia. 

 1884. Bellerophon percarinatus. White, Geol. Surv. Indiana, 13th Rept., p. 158, pi. .S3, figs. 9-14. 

 Coal Measures: Indiana. 

 . Bellerophon percarinatus. Claypole, Proc. and Coll. Wyoming Hist, and Geol. Soc, vol. 2, pt. 2, 

 p. 246. 

 Lower Coal Measures: Wilkesbarre, Pa. 



1887. Bellerophon percarinatus. Herrick, Sci. Lab. Denison Univ., Bull., vol. 2, p. 17, pi. 2, fig. 14. 



Coal Measures: Flint Ridge, Ohio. 



1888. Bellerophon percarinatus. Iveyes, Acad. Nat. Sci. Philadelphia, Proc, p. 234. 

 Lower Coal Measures: Des Moines, Iowa. 



1895. Belhrophoii percarinatus. Keyes, Missouri Geol. Surv., vol. 5, p. 153, pi. 50, figs. 2a-f. (Date 

 of imprint 1894.) 

 Upper Coal Measures: Kansas City, Mo. 

 1897. Bellerophon percarinaius. Ulrich, Geol. Nat. Hist. Surv. Minnesota, Final Rept., vol. 3, pt. 2, 

 p. 853. 

 Coal Measures. 

 1899. Bellerophon percarinatus. Girty, U. S. Geol. Surv., Nineteenth Ann. Rept., pt. 3, p. 592. 



The material studied, though poorly preserved, is sufBciently well characterized 

 to show that it certainly belongs to the group of Bellerophon jyercarinatu^s. Whether 



