444 GEOLOGY OF THE BLACK HILLS. 



ated on the angles of the flattened dorsum, but become obsolete on the 

 outer third of the volution, where the dorsum is also sharply rounded. The 

 inner ranges consist of smaller nodes, and are situated near the border of 

 the umbilicus. The septa closely resemble those of the typical form of 8. 

 nodosus Owen, but are arranged so closely as to interfere or interlock with 

 each other. 



This variety differs from the typical form of 8. nodosus in the same 

 direction, but still more widely than the variety brevis Meek, being more 

 compressed laterally, more distinctly flattened on the back of the body 

 whorl, and the costse are still finer than in that variety, while the deflec- 

 tion is less extreme and the ventral border of that part more curved. 



Fsrmation and locality. — This variety has been obtained from beds of 

 the Fort Pierre Group, at the top of the gray shales of that formation on 

 the Cheyenne River, near Rapid and French Creeks, and also from beds 

 which contain a mingling of the fossils of this and the succeeding group on 

 Old Woman Fork, Black Hills. 



ScapMtes nodosus var. plenus, M. & H., Proc. Acad. Nat. Sci. Phil., 1860, p. 420; and Pal. 

 U. S. Geol. Surv. Terr., p. 429, PI. 26, fig. 1. 



This form differs from the typical S. nodosus in being much more ven- 

 tricose as well as larger, while in the strength of the costse it corresponds 

 closely to that one. The nodes are represented in the figures given as 

 being round and somewhat tumid. We have not recognized this form among 

 the collections brought from the Black Hills by Professor Jenney's party. 

 Mr. Meek cites the Yellowstone River, one hundred and fifty miles from 

 its mouth, as the locality of the specimens referred to this variety. 



SCAPHITES WABEENL 



Plate 13, figs. 1-4. 



Scaphites warreni M. & H, Proc. Acad. Nat. Sci. Phil., vol. 12, pp. 177, 420. 

 ScapMtes warreni M. & H., Smithsonian Check List Invert. Foss., p. 24. 

 Scaphites warreni (M. & M.) Meek, Pal. IT. S. Geol. Surv. Terr., p. 420, PI. 6, fig. 5. 



Shell of moderate size, transversely subovate in general form ; regu- 

 larly coiled in the earlier stages of growth ; the volutions rounded and 



