MESOZOIC FOSSILS. 621 



TANCREDIA ? KNOWLTONI 11. Sp. 

 PI. LXXIII, fig. 6. 



Shell small, obliquely subovate in outline; beaks prominent, sub- 

 median; dorsal margin behind the beaks descending rapidly to the broadly 

 rounded posterior end, which is most prominent below; anterior end 

 rounded, most prominent above, somewhat more narrow than the posterior 

 end; ventral margin gently convex; posterior umbonal ridg*e with a 

 tendency to become angular; surface marked by fine lines of growth. 



Length, 15 mm. ; height, 12 mm. ; convexity of single valve, about 2 mm. 



The hinge is unknown and the generic reference is based merely on 

 external form. The species seems to be congeneric with the species from 

 the Black Hills referred to Tancredia by Whitfield, though the difference 

 in outline prevents its reference to any of his species. 



From shales on north side of road near Sentinel Butte, collected by 

 Prof. F. H. Knowlton. 



Protocardia shumardi Meek and Havden. 



Carclium shumardi Meek and Hayden, 1800: Proc. Acad. Xat. Sci. Phila., p. 182. 

 Protocardia shumardi Meek and Hayden, 186.5: Pahuont. Upper Missouri, p. 98, 

 figs. A and B in text. 



The collection contains several specimens of a small Protocardia that 

 seem to belong to this Black Hills Jurassic species. They have the out- 

 lines of that species, though some of the shells are nearly twice as large as 

 the figure of the type. The body of the valve is marked only by fine 

 lines of growth, and the posterior area bears about eight to twelve radiating 

 ribs that are broader than the interspaces. 



Collected on the divide between Fawn Creek and Gallatin Valley; 

 head of north fork of Fawn Creek ; Sentinel Butte, and Cinnabar Mountain. 



Cyprina? cinnabarensis n. sp. 

 PI. LXXIII, figs. 7 and 8. 



Shell of medium size, moderately convex, subcircular in outline, with 

 prominent submedian beaks; dorsal margin excavated in front of the beaks, 

 gently sloping behind, and in both cases passing gradually into the rounded 

 ends; posterior end in some individuals slightly straightened, so as to become 



