399 



Costa Rica Miocene — Olsson 



227 



A recent West Indian species but also common as an Up- 

 per Miocene and Pliocene fossil along the Atlantic coastal plain 

 of eastern United States. The ribs number 24 to 27 in front of 

 the umbonal angle. Dall has described a Cardiiim {Fragum) 

 gatunensis from Gatun, on which the ribs number only 16 in 

 front of the truncation and 10 behind. 



Gahm Stage: Port Lwio7i. 



Section TRI60NI0CARD1A Dall 



Cardium heredium, n. sp. Plate 27, figure to 



Shell small, solid, oblique, convex and subquadrate; strong- 

 ly carinate on the posterior-umbonal slope and truncated; umbos 

 high and prominent; shell sculptured anterior to the truncation 

 with 12 or 13 strong ribs, separated by interspaces about >^ to 

 Yi as wide; there are 7 or 8 smaller ribs on the posterior trun- 

 cation; the interspaces are finely sculptured with small, elevated 

 cross- threads; the anterior set of ribs on the type specimens are 

 wide, subequal and smooth; the posterior are unequal, with the 

 three, bordering the umboal angulation much the smaller and 

 bearing small and scattered pustules; on the posterior ribs where 

 the pustules are lacking, are small dot-like depressions. 



Height 11.50, length 11.50, diameter 6.00 mm. 



This species approaches the Cardium apatetiaun Dall from 

 the Oak Grove sands of Lower Miocene age in Florida. It dif- 

 fers by its more oblique umbos and proportionately higher shell. 

 The pustules are variously developed and on some shells are 

 more strongly developed and ma}^ also appear on some of the 

 ribs anterior to the truncation. These more strongly scalptured 

 shells may prove wath more material to belong to another 

 species. 



Gatun Stage: Rio Betey. 



Banana River. 

 Estrella River. 



