424 GEOLOGY OF TUE BLACK HILLS. 



Formation and locality. — In Cretaceous beds near French Creek, Black 



Hills; thouj^ht by the collectors to have come from the upper part of the 



Fort PieiTC' Group, but the species is given by Mr. Meek only as from the 



Fox Hill's beds, No. 5. 



Genus FUSUS Lam. 



FUSUS SHUMAEDI. 



Plate 12, figs. 7, 8. 



Fmu8 Shumardii H. & M., Mem. Am. Acad. Arts aud Sci., voL v, 2d ser., No. 391, PL 

 3, fig. G. 



Shell small, with a moderately elevated spire and rather short rostral 

 beak ; volutions about six, strongly ventricose, and marked by compara- 

 tively strong, slightly oblique, vertical costaj or folds, which are directed 

 forward on the lower part of the upper volutions and again recurved below, 

 as seen on the body whorl, and also by finer striae of growth between the 

 folds. The folds are crossed by numerous elevated revolving lines, with 

 wider interspaces ; suture well marked and distinct ; aperture obliquely 

 ovate, obtusely pointed above, and continued below into the short, narrow, 

 rostral canal ; columellar lip slightly thickened, but without visible folds 

 or plaits 



The specimen used is imperfect at both extremities and much of the 

 surface shell removed ; enough remains, however, to furnish the specific 

 characters. The species may possibly belong to Mr. Meek's genus Trachy- 

 friton; but although the vertical folds are distinctly marked where the shell 

 is entirely removed, there is no evidence of revolving lines on the spaces 

 between them, as required in the diagnosis of that genus. 



Formation and locality. — In a ferruginous sandy limestone on the east 



fork of Beaver Creek, Black Hills, associated with fossils referred to the 



fort Benton Group. 



FUSUS CHEYEKNENSIS. 



Plato 12, fig. 9. 



Fusm cheyennemin Wliitf., Prelim. Kept. PaL Black Hills, 1877, p. 37. 



Shell small, spire slender and elevated ; the number of volutions un- 

 known, but probably six or more, strongh' rounded, the last one somewhat 

 ventricose above the middle, but attenuate below ; aperture semi-ovate, being 



