196 UNITED STATES GEOLOGICAL SURVEY OF TI1E TERRITORIES. 



being a little shorter and faintly subtruncated, with a very obscure flexure, 

 and most narrowly rounded below; dorsal outline sloping gently in both 

 directions from the beaks, the posterior slope being a little convex in outline, 

 and the anterior nearly straight above ; beaks depressed, compressed, and 

 placed a little behind the middle ; muscular impressions moderately distinct, 

 the posterior one being broader than the other; pallial sinus very deep, or 

 extending slightly beyond the middle, nearly horizontal, and rather broadly 

 rounded. Surface with only fine lines of growth. 



Length, 0.84 inch; height, 0.47 inch ; convexity, about 0.15 inch. 



This shell is much like Tellina scilula, Meek and Hayden, from the 

 upper member of the Upper Missouri Cretaceous series; but on comparison 

 it is found to be proportionally more depressed, while its pallial sinus is very 

 different, being much broader and more obtusely rounded at the end. 

 Impressions of its surface in the matrix also indicate less strongly-defined 

 lines of growth. Casts show what may possibly be faint traces of a posterior 

 lateral tooth in one or both valves. 



Locality and position. — Twelve miles southwest of Salina, Kansas ; in 

 the Dakota group of the Upper Missouri Cretaceous series. 



Tell ina (Pcronaea!) cqu ilatc ralis, M & H. 



Plate 39, tigs. 5, a, b, c. 

 Tellina equilateralis, Meek and Haydon (1B5G), Proceed. Acad. Nat. Sci. Pliilad., 82. 



Shell subelliptical, rather thick, moderately compressed; right valve 

 slightly more convex than the left ; anterior end rounded ; anal extremity 

 rounded, or very faintly truncated and slightly 'flexed to the left; basal mar- 

 gin broad, semi-elliptical in outline, laterally curved so as to present a slight 

 concavity on the left side ; dorsal border declining gradually from the beaks 

 toward the extremities, the posterior slope being more convex than the 

 anterior, and rather distinctly excavated for the reception of the ligament; 

 posterior fold or ridge not very distinctly marked ; beaks small, not much 

 elevated, located near the center of the shell ; surface marked by small, 

 irregular, concentric wrinkles, and fine, rather obscure lines of growth. 



Length (of largest specimen seen), 1.77 inches ; breadth, 0.59 inch ; 

 height, LOG inches. 



Associated with the specimens of this species, a few internal casts were 



