174 STUDIES IN GEOLOGY, No. 3 



la (Cuneocorbula) pro pin qua n. sp. 

 PLATE X Fig. 16. 



Shell ovate, somewhat produced, of good size for the 

 section. Anterior margin somewhat produced, rounded; 

 ventral margin elliptical, ascending posteriorly; posterior 

 ( dorsal) margin nearly straight. Shell pointed posteriorly. 

 Umbones inconspicuous, anterior in position. General sur- 

 face convex except posteriorly, where a narrow concave 

 area exists between the characteristic keel. The ventral 

 surface of the left valve is squared off. The extreme pos- 

 terior portion of the left valve (and possibly the right 

 specimens broken) is drawn out to form a horizontal chisel- 

 like point inside the end of the rostral keel. Sculpture of 

 fairly regular, fine concentric ribs which are slightly more 

 prominent and more irregular on the right valve. On the 

 chisel-like point the sculpture is of fine longitudinal lines. 

 No lunule, and small trace, if any, of an escutcheon is visible 

 on the material examined. Length, 15; height, 9; diameter, 

 5.5 mm. 



This species is similar in many characteristics to C. fabi- 

 formis. It differs primarily in being much larger and in 

 having the posterior end more pointed. The flattened pos- 

 terior point is not present in fabiformis. It is also similar to 

 C. kaghriana Dall, 202 from the Orthaulax bed at Ballast 

 Point, Florida, but is longer, more pointed, and has finer 

 sculpture. Otherwise the resemblance is close. 



Variegated. Quebrada Tusillal. 



Corbula (Cuneocorbula) bravoana n. sp. 

 PLATE X Fig. 17. 



Shell of good size, distinctly triangular, less rounded than 

 the usual Cuneocorbulas. Anterior margin straight dorsally, 

 somewhat abruptly curved below. Ventral margin nearly 

 straight, ascending slightly throughout its length; posterior 



U. S. Nat. Mus. Bull. 90, p. 155, pi. 21, figs. 4, 5, 1915. 



