226 ANNALS NEW YORE ACADEMY OF SCIENCES 



fines the anterior third of ttie shell. The beak is about one third the width 

 back from the front margin, small, strongly incurved. The anterior extremity 

 is nasute. The hinge is straight, about one half the entire width. The lower 

 margin is gently and regularly convex. The posterior outline is gently con- 

 vex, truncating the shell with a slight obliquity such as to make the posterior 

 superior angle somewhat obtuse and the posterior inferior angle somewhat 

 acute. The anterior outline is abruptly rounded and concave under the beak. 

 The surface is marked by very fine subequal concentric stride. 



Edmondia equilateralis sp. nov. 



Shell very small, transversely elliptical. Width slightly less than one half 

 the greatest lieight. Hinge line straight, about one half the width. Basal 

 margin gently convex. Anterior and posterior outlines strongly and regularly 

 curved, nearly equal, gradually merging with the outlines above and below. 

 Convexity rather high and regular. Umbonal ridge indistinct. Beak small, 

 depressed, scarcely projecting beyond the hinge line, only slightly posterior to 

 the margin. 



Surface marked by fine, strong, sharp, subequal concentric lirse. The in- 

 ternal structures are not known, and the reference to the genus Edmondia is 

 therefore provisional. 



Cardiomorpha inflata sp. nov. 



Shell of medium size, the largest specimen having a length along the um- 

 bonal ridge of 29 mm. Convexity high, equal in the two valves. Upper and 

 lower margins gently convex, somewhat converging toward the front. Pos- 

 terior margin subrectilinear, strongly oblique, merging with the cardinal bor- 

 der in a gentle curve and with the inferior border in an abrupt turn. Ante- 

 rior end subtruncate. Beaks nearly terminal. Inferior-anterior angle sharply 

 rounded. Convexity high, especially along the broad, undefined umbonal 

 ridge, from which the shell descends abruptly to the hinge anteriorly and more 

 gently posteriorly. A distinct, though ill defined, sinus passes diagonally 

 across the shell just in front of the umbonal ridge, meeting the lower margin 

 about midway. 



Surface marked by numerous closely arranged subequal lamellose lines. 



Leda stevensiana sp. nov. 



The size is small, a larger specimen when complete having a width of 

 10 mm. and a smaller a width of only 7 mm. The greatest height is one 

 half the width. The beak is situated about one third the width back from 

 the anterior outline. The lower margin is gently convex, the posterior exten- 

 sion long and subangular, the anterior end symmetrically rounded. The upper 

 posterior border is gently concave. The convexity is moderate and the surface 

 marked by very fine, somewhat inosculating lime. 



Of this species, our collection contains but two specimens, both right 

 valves, one of them complete but small and failing to show the sculpture, 

 the other larger and retaining the sculpture, but imperfect at the ante- 

 rior end. 



