4:(!4 CARBONIFEROUS FORMATIONS AND FAUNAS OF COLORADO. 



18";>. XatirnpKis altoyiensix. Meek and Wortheri, Geol. Surv. Illinois, Rept., vol. 5, p. 595, pi. 28, tif.'s. 

 11a, lib. {Naticopsis altonenais? on description of plates.) 

 Coal Measures: Macoupin County, 111. 

 18.H1. A^dliraps-in iilliiiiniKi.i. White, U.S. Geog. Geol. Snrv. W. 100th Mer., Rept., vol. 3, Supp., Appen- 

 liix, p. x.xxv, pi. S, lig. 6a. 

 Carboniferous: Near Taos, N. Mex. 



Only four specimens have been referred to this species, and they are, unfor- 

 tunately, in an imperfect condition. One of them, from station 2223, in the Rico 

 (juadrang-le, closely resembles the elongate shell upon which the original description 

 was based. It is, however, considerably larger, having a length of not less than 55 

 nun., and possibly belongs to the variety which Meek and Worthen figured under 

 the varietal name of giganteus." Another shell, from station 2340 in the same 

 area, is more compact and has the sha'pe depicted b}' Meek and Worthen's figures 

 11a and lib, which the_v identify as JV. altonensisf It is about the size of the 

 specimen represented by these figures and is smaller than the example previously 

 mentioned. 



Two shells from Sinbads Valley, whose mutual relations are not quite certain, 

 have been doubtfully identified with J^. altonensh. They are internal casts, not very 

 perfect at that, and their real aflinities are obscure. It is possible that one of them 

 may be a Soleniscus, related to S. pmiderosvs. 



Locality and horizon. — San Juan region (stations 2226, 2310); middle jDortion of 

 the Hermosa formation and in the Rico formation. Dolores River region, Sinbads 

 Valley (station 2285); top of the Hermosa formation. 



Naticopsis monilifeka White. 



1880. Naticopsis monilifera. White, TJ. S. Geol. Geog. Surv. Terr., Twelfth Ann. Rept., for 1878, pt. 



1, p. 168, pi. 42, figs. 3a-c. 

 Upper Coal Measures; Pleasant Hill, Cass County, Mo. 



1881. Xaticopsis monilifera. White, U. S. Geog. Geol. Surv. W. 100th Mer., Rept., vol. 3, Supp., Appen- 



dix, p. xxxiv, pi. 3, figs. 3a-d. 

 Carboniferous: Xear Taos, N. Mex. 

 1895. Pleurotomaria moniUfem. Keyes, Missouri Geol. Surv., vol. 5, p. 144. (Date of imprint, 1894.) 

 Upper Coal Measures: Pleasant Hill and Kansas City, Mo. 



My specimens are so much exfoliated as to be reduced almost to the condition 

 of internal casts. The beaded ornamentation on the upper portion of the peritreme 

 near the suture line is plainly visible, but otherwise, from such evidence as is avail- 

 able, I judge that the sui'face was without ornamentation. In general conformation 

 these specimens are in the closest agreement with White's figures and descriptions, 

 and as they also agree with the specimen from Taos, N. Mex., which he figures as 

 JHf. monilifera, it is with little hesitation that they are referred to that species. 



iGeol. Surv. Illinois, Rept., vol. 5. 1873, pi. 28, figs. 12a, 12b. 



