37 



small ; beak closely incurved down to the umbo of the dorsal valve. 

 Dorsal valve some^Yhat more strongly convex than the ventral; the 

 outline on a side view nearly parallel with the plane of the lateral margin 

 for about two-thirds the length from the front, then abruptly curved 

 down to the beak. Owing to the depth of the sinus the front margin, on a 

 side view, is nearly squarely truncated for about half the depth of both 

 valves. The mesial elevation is either uniformly convex or a little 

 flattened in the middle, usually gently sloping but sometimes abruptly 

 elevated at the sides of the margin. It becomes obsolete at one-half the 

 length of the shell. 



Surface with thirty to forty rounded or sub-angular ribs (counted at the 

 margin.) Some of these on the mesial fold of the dorsal valve, and in the 

 sinus of the ventral valve, are undivided throughout their whole length. 

 On each side of the fold and sinus the ribs are bifurcated at various 

 points between the beak and front margin. 



In one specimen, from which the shell has been partially removed, the 

 cast of the interior of the dorsal valve shews a mesial septum extending 

 about one-third of the length from the beak. 



Length of a specimen of average size, thirteen lines ; width, sixteea 

 lines ; depth of both valves, nine lines. 



This species seems to be rare, as only about a dozen specimens have 

 been collected. 



Locality and Formation. — Indian Cove, Gasp^ : Gasp<3 limestone, No^ 



8. 



Collector.— Bell. 



Khynchonella Dryope. (N. sp.) 



Plate 3 A. figs. 1, la, 16, Ic. 



Descrijytion. — Subcircular or subpentagonal ; apical angle varying from 

 about 95 ^ in the smaller specimens to 130 ^ in the larger. Slope on 

 each side of the beak concave or nearly straight for two or three lines, 

 then slightly convex ; sides rounded ; front margin, with a portion in the 

 middle about equal to one-third the width, either straight or slightly con- 

 cave. In the larger specimens the greatest width is about the mid-length ; 

 in the smaller somewhat nearer the front. "Width of a large specimen, 

 thirteen lines ; length, eleven lines ; depth of both valves near the front mar- 

 gin, eight lines. Ventral valve varying from slightly to moderately convex ; 

 a portion on each side of the mesial sinus flat or even slightly concave near 

 the front margin; umbonarrow ; beak Incurved down to the umbo of the dor- 

 sal valve. The mesial depression is rather less than one-third of the wholo 



