GASTEEOPODS. 197 



Strophostylus remex (WHITE). 



Plate lv, figs. 7a-b. 



Naticopsis remex White, 187G : Geol. Uinta Mis., p. 109. 

 Naticopsis remex White, 18S3 : U. S. Geol. aad Geog. Sur. Terr., p. 139, 

 pi. xxxiv, fig. 6. 



Shell rather small, partially uncoiled toward the aperture ; 

 whorls about four in number, very convex; spire short. 

 Aperture sub-circular; lip sharp. Surface smooth, or only 

 marked by lines of growth. 



Horizon and localities. Upper Carboniferous, Upper Coal 

 Measures: Kansas City. 



The form under consideration is not of uncommon occur- 

 rence in western Missouri and eastern Kansas, and appears to 

 be identical with the shell described by White as Naticopsis 

 remex. Well-preserved shells show plainly that this species is 

 a member of the group represented in the Coal Measures by 

 Platystoma peoriense of McOhesney and has none of the dis- 

 tinguishing characters of Naticopsis as at present understood. 

 The last whorl is somewhat uncoiled, just as in certain Upper 

 Silurian species from Waldron, Indiana. 



Strophostylus peoriensis (M.CCHESNEY). 



Plate lii, tig. 6. 



Platy sterna peoriense McChesney, 1860: Desc. New Pal. Foss. , p. 62. 

 Platystoma peoriense McChesney, 1867: Trans. Chicago Acad. Sci., vol. 



I, p. 49, pi. ii, figs, lla-b. 

 Strophostylus peoriensis Keyes, 1890: Am. Naturalist, Vol. XX [V, p. 115, 



pi. xxxiii, fig. 7. 



Shell of medium size, thin, somewhat elongated; volu- 

 tions about two in number, contiguous, enlarging rather rap- 

 idly, the outer one quite ventricose ; spire depressed, scarcely 

 rising above the general level of the whorls; suture rather 

 deep, distinct. Aperture ovate. Surface glabrate, with very 

 fine lines of growth. 



Horizon and localities. Upper Carboniferous, Upper Coal 

 Measures : Kansas City. 



