176 



Bulletin 39 



348 



A much smaller species than the preceding and differing in 

 its more anterior beaks, depressed shell and heavier concentric 

 sculpture as well as in other characters. It is probably the shell 

 which Dall refers to as having fragments of from the Pliocene 

 of Limon. But a single perfect specimen was collected 



Gatun Stage; Port Limon. 



Genus YOLDI A Moller 



Yoldia bocasensis, Plate 28, figures 21, 22 



Shell small, thin, ovate- elliptical in form; beaks situated 

 slightly in front of the middle; valves moderately convex; both 

 the anterior and posterior extremities are broadly rounded and 

 connected by the gentle curve of the basal or ventral margin; the 

 umbos are very small but distinct and lie just above the greatest 

 convexity of the valves; surface smooth, polished with no other 

 sculpture than the incremental growth-lines; chondrophore dis- 

 tinct, scarsely oblique and bordered on each side by an equal num- 

 ber of V-shaped hinge-teeth; the anterior set contains about 14 

 teeth, which are very small next to the chondrophore becoming 

 progressively larger distally, the posterior set with 13 or 14; the 

 pallial sinus is indistinct, but rather large, broad and extends 

 nearly to the middle of the valve. 



Length 13.00, height 7.00, semidiameter 2.25 mm. 



9.50 5.50 1.50 mm. 



A fairly common species in the clay beds of Bocas Island 

 where it is associated with a fauna of rather deep water charac- 

 ter. It has much the form of certain deep-water Yoldiella but 

 the interior of the valves show an indistinct but deep and wide 

 pallial sinus. 



Gabb has described from the Miocene of Santo Domingo, a 

 Yoldia ovalis, which has never been figured and its description is 

 very meager and insufficient. 



Gatun Stage: Bocas del Toro. 



