214 



Bulletin 39 



386 



numbering about 10; the interspaces carry irregular, finer, con- 

 centric lines; lunule narrowly lanceolate, with the escutcheon 

 narrow and smaller; interior of shell cavity shallow, with a mod- 

 erately heavy hinge. 



Length 3.25, height 3.25, diameter of one valve i.oo mm. 



A small, rare species, somewhat like the C, Guppyi Dall of 

 the Miocene of Jamaica, but more trigonal, with more central 

 beaks and somewhat different sculpture. The sculpture and 

 form are very similar to specimens of C. galvestone?isis Harris in 

 the Cornell Collection from the Chesapeake Miocene of York- 

 town, Va. This latter species is generally much worn but per- 

 fect specimens have a coarse concentric sculpture like that of 

 lunulatus Conrad. The Costa Rican shells are however very 

 much smaller. 



Gatun Stage: Middle Creek, C. R. 



Coll. /, East Grape Point Creek. 

 Vl^ater Cay, Panama. 



Genus CARDITA, (Bruguiere) Lamarck 



Cardita caribbeanensis, n. sp. Plate 26, figure 22 



Shell small, moderately convex, elongate, its length a little 

 less than twice its height; beaks very near the anterior end are 

 small but distinct; an umbonal ridge extends from the beaks to 

 the posterior- ventral extremity and along which and bordering 

 the ribs are largest; the right valve with about 20, hight, narrow 

 and sharply nodulose ribs, separated b}^ wide, triangular, smooth 

 interspaces; 6 of the ribs are situated on the posterior-dorsal 

 submargins, and of which the 4th and 5th from the dorsal mar- 

 gin are much smaller than the others; of the remaining ribs, the 

 largest are found on the umbonal ridge, and become progressive- 

 ly smaller anteriorly; lunule small but distinct; hinge of the 

 right valve that of typical Cardita, with 3 cardinal teeth of which 

 the middle one is much the largest, no laterals; ventral margin, 

 internally fluted in harmony with the external ribs. 



