OE DENISON UNIVERSITY. 57 



the layer a few feet below congl. I. The species is also found forty 

 feet below congl. I, at Union Station, in large, finely preserved speci- 

 mens, a left valve measuring in length, 25 mm, in width 23.5 mm. 



Sbrehlopterin squarun, sp. n. 



(Plate VII, Fig. 14.) 



Smaller or medium size, with extended hinge-line and ovate out- 

 line. Left valve quadrately ovate ; length and height about eijual ; 

 hinge about three- fourths the length ; anterior outline nearly straight, 

 slightly convex below and concave at the ear ; posterior outline gently 

 and uniformly convex ; anterior wing largest, nearly rectangular, not 

 very distinctly separated from the body; moderate posterior ear ob- 

 tusely angular, passing without interruption into the general surface of 

 the body; surface slightly convex, ornamented only by fine, cfwl.-.l 

 imbricating lines, epidermis very thin. Shales below congl. 1 



Th\s species is considerably smaller than the average sj)ecimi.*ns 

 of S media and is more broadly ovate, with a longer hinL'c-line. No 

 traces of radiating striae could be seen. 



Strchlopterifi o^rricilis, ^i'- '^ 

 (Plate VII, Fig. 12.) 



Shell of medium size, elongate, with very short hinge. 



Left valve narrowly elliptical, length four-fifths the height, hinge 

 less than half the length ; posterior margin a uniform slight curve to 

 the almost obsolete ear : anterior margin very abruptly flexed at the 

 umbonal slope to the short, obtusely triangular ear; surface convex, 

 ornamented by concentric and obscure radiating lines. Free-stone of 

 middle Waverly ( ?) This species resembles the larger form of S. media. 

 but is at once distinguished by its nnrrow.-r form and short hinge-line. 



Pernojxctrn slniiiKirdidnns, Win. ? > 

 (Plate XII, Figs. 13-v) 

 A considerable number of nearly perfect valves are represented 



