398 GEOLOGY OF THE BLACK HILLS. 



such point. The most marked and striking difference between this form 

 and 7". sagensis is in the size and form of the beak of the shell, these being 

 small and compressed, those large and prominent. Several specimens of 

 each valve are present in the collection before us. 



Formation and locality. — In Cretaceous beds of the Fort Pierre Group, 

 on the Cheyenne River, near Rapid Creek ; on Old Woman Fork, and at 

 top of gra} r shales near mouth of Rapid Creek, Black Hills. 



INOCEEAMUS VANUXEMI, var. ? 



Plate 7, fig. 10. 



The single individual represented by Fig. 10, Plate 7, presents such a 

 marked departure from the characters of the other specimens in the collection, 

 that we do not feel certain that it belongs to the same species, although of 

 the same type. The form is erect, the height considerably exceeding the 

 length of the valve, giving a broad ovate form, slightly truncate above by 

 the hinge line, which is quite short, and the beaks compressed and entirely 

 within the limits of the outline. The concentric undulations are very simi- 

 lar to the more closely arranged ones on the forms which we have referred 

 to I. vanuxemi, and also to the form figured by Mr. Meek as I. proximus 

 Tourney. The specimen is a left valve and quite depressed convex, although 

 it has suffered accidental compression. A part of the right valve is also 

 preserved, but in a much more mutilated condition and more compressed, 

 so that we cannot judge of the convexity with certainty. Owing to the 

 above-mentioned differences we have hesitated to include it under the same 

 specific designation until further collections shall demonstrate the fact. 



Formation and locality. — Near the top of the gray shales of the Fort 

 Pierre' Group, on the Cheyenne River, near Rapid Creek, Black Hills, 

 Dakota. 



INOCERAMUS BARABLNI. 



Plate 7, fig. 7 ; Plate 9, fig. 8. 



Inoceramus barabini Morton, Synop. Org. Bern. Oret. N. A. 1834, p. 62, PI. 17, fig. 3. 

 Inoceramus cripsii var. Barabini (Morton) Meek, Pal. IT. S. Geol. Surv. Terr., p. 49, PI. 



13, fig. 1 ; PL 12, fig. 3. 

 Inoceramus gibbus Tourney, Proc. Acad. Nat. Sci. Phil. 1854, vol. vii, p. 170. 

 Inoceramus cuneatus M. & H., Proc. Acad. Nat. Sci. Phil. 1860, p. 181. 



