226 Bulletin 39 398 



Cardium ( Trachycardiurn) dominicense ^ro^-n and Pilsbry, 191 1, Proc. 

 Acad. Nat. Sci. Phila., vol. 63, p. 367. 



A large species abundant in the Canal Zone but usually only 

 as internal casts. It appears to be rare in Costa Rica, our col- 

 lection containing onl}^ a few fragments of a large individual 

 froni East Grape Point Creek. It is distinguished not only by 

 its large size, but very numerous (60 + ) fine ribs. 

 Gatun Stage: Gatun, C. Z. 



East Grape Point Creek, C. R. 

 Safjote, C. R. {Gabb) 



Cardium costaricanum, n. sp. Plate 27, figure 3 



Shell ovate, solid, inflated; umbos wide and full with high 

 beaks; sculpture of about 24 strong ribs, rounded or subtrian- 

 gular in section with their apex leaning posteriorly except those 

 on the posterior slope which lean anteriorlj^; interspaces narraw, 

 formed by the sides of the ribs; the ribs are mostly smooth ex- 

 cept those on the anterior half of the shell which have their pos- 

 terior side more or less granulated; this granulation is found al- 

 so on a few of the central ribs near their ventral margin; hinge 

 narrow; internal margin fluted in harmony with the external 

 ribs. 



Length 24.50, height 34, semi-diameter 15 mm. 



This species is not uncommon in Costa Rica and may easily 

 be confused with the C. dominicanuvi Dall. It differs in its 

 larger side, narrow umbos, more pointed beaks and more flatten- 

 ed ribs. 



Gatun Stage: Coll. /, East Grape Point Creek. 



Subgenus FRAGUIVI, Bolton 



Cardium medium Linnaeus Plate 27, figure 6 



Cardinm mediutn Ivinnseus, 1758, Sys. Nat. ed. 10, p. 678. 



Cardium medium Reeve, 1844, Conch. Icon., Cardium, pi. 6. fig. 



30- 

 Cardium {Fragum) medium Dall, 1900, Trans. Wagner Free Inst. 

 Sci., vol. 3, pt. 5, p. iioi. 



