220 Bulletin 29 384 



large Vs with apices directed upwards. The sculpture is strong- 

 est on the central part of the valves and is weaker posteriorly. 

 Cardinal teeth in the left valve two, the anterior strongly bifid. 

 Length 14, altitude 13, semidiameter 4 mm. The first Petricola 

 ever found in- the Santo Domingo blue clays. 



Locality. — (Exp'd '16) Zone H, Rio Cana at Caimito. 

 (Boring in coral). 



Petricola (Rupellaria') riocanensis, n. sp. 

 Plate 37, Figure 12 



Shell ovate, convex, inflated ; very short and rounded an- 

 teriorly, produced and bluntly pointed posteriorly ; radially 

 sculptured with somewhat irregular, sharp ridges which are in- 

 terrupted and rendered more or less discontinuous by the thick- 

 ened concentric resting stages. This species resembles P. typica 

 Jonas now living in the Antilles and found in the Florida Plio- 

 cene, but differs in the following respects: — (i)the fossil is short- 

 er anteriorly ; (2) less produced posteriorly ; (3) the beak is 

 more anterior ; (4) the sculpture more uniform over the shell ; 

 (5) the hinge is weaker. These differences are constant in all 

 our specimens. Length 21, altitude 17, semidiameter 8 mm. 



A recent shell in the Newcomb collection labelled P. robusta 

 Sowerby from the Gulf of California is the Pacific analogue of 

 our fossil. 



Locality. — (Exp'd '16) Zone H, Rio Cana at Caimito. 

 (Boring in coral). 



Genus Tellina Linne 



Tellina riocanensis, n. sp. 



Plate 38, Figure 3 



Shell polished, shining, somewhat inequivalve, the right valve 

 being more compressed than the left, the difference in diameter 

 averaging a millemeter ; left valve gently convex ; the valves 

 are also discrepantly sculptured, the sculpture of the right being 

 stronger. The ornamentation consists of fine, close, flattened 



