rRETACKOUS FOSSILS. 443 



Formation and locality. — In limestone at the top of the gray shales of 

 the Fort Pierre' Group, on the Clieyenne River, near Rapid Creek, Black 

 TTills, Dakota. 



SCAPniTES NODOSUS var. BEE VIS. 



Plate 13, fi-;-. 8, 9. 



Scaphites nodostis var. hrevis Meek, Pal. U. S. Geol. Surv. Terr., j). 426, PI. 25, fig. 1. 



This variety differs from the typical form of S. nodosus Owen, in being 

 less ovate, the deflected portion being rather shorter, and in the more com- 

 ])ressed form of the shell as seen in profile, and also in the narrowly 

 ronnded dorsum. The costse are somewhat finer on all of the examples we 

 have seen, and the nodes smaller, and not commencing at so early a stage 

 of growth ; while the inner range of nodes is usually obscure or only seen 

 on the deflected part of the body volution. The most conspicuous dififer- 

 ences are the compressed form of the shell and the more narrowly rounded 

 dorsum. 



Formation and locality. — The examples of this variety are found asso- 

 ciated with the typical form at the top of the gray shales of the Fort Pierr^ 

 Group, Cheyenne River, near Rapid Creek, Black Hills, Dakota. 



SCAPHITES NODOSUS var. QUADRANGULAEIS. 



Plate 13, figs. 10, 11. 



Scaphites nodosus var. quadrangularis Meek, Pal. U. S. Geol. Surv. Terr., p. 428, PI. 25, 

 figs. 2-4. 



Shell discoidal, with latterally compressed volutions, and the dorsum of 

 the deflected part of the outer volution somewhat flattened. General out- 

 line of the shell slightly ovate, the outer coil being somewhat deflected from 

 the general curvature of the involute parts, and the extremity again recurved, 

 so as to bring the ventral margin nearly or quite to the dorsal limit of the 

 preceding volution, and the margin of the aperture nearly at right angles 

 to the ventral line of the deflected portion. 



Surface of the sl:i^ll ornamented by fine, somewhat sinuous, transverse, 

 bifurcating costse with narrow concave interspaces, and also by two ranges 

 of nodes on a part of the last volution. The outer ranges of nodes are situ- 



