4(52 CAKHONIKKHorS FORMATIONS AND FAUNAS OF COI.OHADO. 



less iioiirly scvciul of those described I'roiii dillcrcnt horizons in the \Vost(M'n States, 

 hut after a eritieal coiiiparison T havi^ heeii unahle to identify it witli any of them.''' 

 It is, therefore, witli hesitation that I adopt the synonymy sugf^-ested h\' Keyes. My 

 reasons for using- the g-eneric term Phifycemii instead of CajmJm will be found stated 

 on a ])revious page of this i-e-jwrt. 



Ldcalit If and horizon. — San Juan region (stations 2218, 2279); lower and upper 

 portions of the llermosa formation. 



STROPHOSTYLUS Hall, 1869. 

 Strophostylus of. NANUS Meek and Worthen 



18H0. Plaiyosloma nana. Meek and Worthen, Acad. Nat. Sci. Philadelphia, Proc, j). 46.'!. 



Upper Coal Measures: Springfield, 111. 

 1861. Naticox>sis nana. Meek and WOrthen, Acad. Nat. Sci. Philadelphia, Proc, p. 148. 

 1866. N'aticopsis nana. Meek and Worthen, Geol. Surv. Illinois, Kept., vol. 2, p. 365, pi. 31, tigs. 4a, b. 



Upper Coal Measures: Springfield, 111. 

 1875. Naticopsis nana. White, U. S. Geog. Geol. Surv. W. 100th Mer., Kept., vol. 4, p. 159, pi. 12, tigs. 

 4a, b. (Whole volume pubhshed in 1877.) 



Carboniferous: Camp Cottonwood, near Spring Mountain, Lincoln County, Nev. 

 1884. Naticopsis nana. AVhite, Geol. Surv. Indiana, 13th Kept., p. 162, pi. 36, figs. 6, 7. 



Middle and Upper Coal Measures: Indiana. 

 1888. Naticopsis! nana. Herrick, Sci. Lab. Deni.gon Univ., Bull., vol. 4, pi. 11, fig. 8. 



Coal Measures: Fultonham, Ohio. 

 1891. Naiicopm nana. Keyes, Acad. Nat. Sci. Philadelphia, Proc, p. 257. 



Lower Coal Measures: Des Moines, Iowa. 



1895. Strophostylus nana. Keyes, Missouri Geol. Surv., vol. 5, p. 196. (Date of imprint, 1894.) 

 Upper Coal Measures: Clinton and Kansas City, Mo. 



1896. Naticopsis nana. Smith, Leland Stanford Junior Univ. Publ.; Cont. Biol. Plopkins Seaside Lab., 



No. 9, p. 40. 

 Upper Coal Measures: Sebastian County, Ark. ; 



1896. Naticopsis nana. Smith, Am. Phil. Soc, Proc, vol. 35, p. 250. 

 LTpper Coal Measures: Sebastian County, Ark. 



This little form probably finds its closest American ally in Strophostylus nanm 

 Meek and Worthen, which, though itself a small species, is fairly gigantic when 

 compared with its Colorado relative. The latter rarely exceeds 2 mm. in height, 

 but in configuration it greatly resembles the larger shell. The spire is depressed. 

 There are three volutions, increasing rapidlj^ in size, but the final one is probably 

 not as inflated as in. typical S. nanus. 



Locality and horizon. — Grand River region, Glenwood Springs (station 2193). 



