401 ' Costa Rica Miocene — Olsson 229 



Gatun Stage: Gatun, C. Z. 



Middle Creek. C. R. 

 Rio Betey, C. R. 



Genus PROTOCARDIA, Beyrich 



Protocardia costaricensis, n. sp. Plate 27, figure 13 



Shell small, rather thin, convex; beaks a little anterior to 

 the middle, with high, inflated umbos; the anterior end is wide- 

 ly rounded, the posterior somewhat truncated; the posterior area 

 is well differentiated and occupies the posterior one-third of the 

 shell and is sculptured with numerous small radial threads sep- 

 arated by wider interspaces; these interspaces are finely sculp- 

 tured with cross-threads; anterior of the posterior area the shell 

 surface is sculptured with small radial threads which are fineh^ 

 beaded; on the anterior end of the shell, the beading is more ir- 

 regular and is seen to be made by the concentric sculpture. 



Height 18, length 2t, diameter of the left valve 7 mm. 



This species differs from both P. jamaicensis Dall from the 

 Bowden beds of Jamaica and P. islahispaniolcB Maury from the 

 Miocene of Santo Domingo by its smaller posterior area. It ap- 

 proaches more closely the Dominican shell but is shorter and 

 more coarsely sculptured. 



The P. Newberryana Gabb from Gatun is based on a large 

 internal cast which is entirelj^ unrecognizable. 



Gatun Stage: Coviadre creek. 



Subgenus LOPHOCARDIUIVI, Fischer 



Protocardia gurabica Maury Plate 27, figures 7-9 



Protocardia gurabica Maury, 1917, Bull. Amer. Pal., vol. 5, p. 377, pi. 



36, fig. 10. 



Shell thin, inflated, a little longer than high and with the 



greatest convexity about the center of the shell; the umbos are 



high, prominent and wide, and project well above the hinge 



