— 48 — 



breadth, 0.55; height, 0.25. Two casts found at base of Pt. Loma, by 

 Mr. Fairbanks, in Cret. A. Fragments of shell also found, which seem 

 to have belonged to this species. 



Astarte semidentata n. sp. (PI. Ill, Figs. 44, 45.) 



Subtrigonal, nearly equilateral; posterior margin slightly curved, 

 obtusely angled; basal little more convex, sharply curved upward 

 anteriorly, half the height of shell; thence deeply excavated to beaks, 

 which bend strongly forward. Lunule long and deep, nearly half the 

 length of posterior margin. Hinge-area broad, the posterior half of it 

 a flat, shallow pit (in the left valve); two strong teeth, with the 

 triangular pit filling anterior half. Lateral teeth very weak, pallial 

 line deeply impressed. Surface slightly convex, with shallow trans- 

 verse grooves near the beaks, becoming obsolete on lower half of disk. 

 Length, 0.90 inch; height, 0.80; diameter about 0.40 (both valves). 

 Three specimens found in Cret. B, in Rose Canon, by Mr. Fairbanks. 

 This species seems to differ more in the hinge than in other features 

 from some living species. Its hinge approaches that of Crassatella, 

 forming a connecting link. 



Crassatella lomana n. sp. (PI. Ill, Fig. 47.) 



Shell large, wedge-shaped, thick, more or less angled on the posterior 

 ■dorsal surface; disk marked only by coarse lines of growth; anterior 

 end truncated nearly at a right angle to dorsum; umbos nearly meet- 

 ing, and dorsal area deeply hollowed behind them. Lunule not 

 impressed, lower half of front obtusely rounded, curving under to the 

 nearly straight basal line, which posteriorly bends upward suddenly 

 to form the narrow wedge-shaped extremity. Dorsal ridges forming 

 obtuse angles from the umbos to the upper edge of wedge. Under 

 layer of shell with fine radiating striaj; inner margins of valves 

 coarsely crenulate. Thickness of shell, about \ inch; at umbos, ^ inch. 

 Length, 3.50 inches; height, 2.20; diameter, 1.38. 



Six specimens were obtained at Pt. Loma, in Div. A, by Mr. Fair- 

 banks. At first I thought it a variety of C. tuscana, which is found 

 with it, but it shows no trace of the concentric ridges of that species at 

 any age, and differs too much in size and form. The radiated under- 

 shell is found in both. I could not obtain a good view of the hinge, 

 but there seems every reason to consider it a Crassatella, in which 

 opinion Dr. C. A. White agrees with me. 



CucuUsea bowersiana n. sp. (PI. V, Figs. 61, 62.) 



Shell large, thick, nearly equilateral; surface smooth, or with coarse 

 lines of growth; valves very convex, sub-truncate posteriorly, but with 

 €dges of valves prominent, rounded; umbonal ridge obtuse, nearly 



