1917.] NATURAL SCIENCES OF PHILADELPHIA. 199 



over which there is a most minute granuhition. Posterior end very 

 short, broadly rounded. Anterior end produced, also Ijroadly 

 rounded, both cardinal teeth bifid. 



Length 1.5, alt. 1.35, semidiameter 0.35 mm. 



Type No. 2758, A. N. S. P. 



Similar to D. minor Dall, but of less oblique, more rounded outline. 



Chione santodomingensis n. sp. 



The shell resembles C. chipolana, but differs as follows. It is 

 shorter and higher, the dorsal and anterior slopes forming a smaller 

 angle. The concentric laminge are widely spaced, and continue 

 over the lunule. The radial sculpture produced by splitting of the 

 ribs is less even. There are fewer concentric ribs than in C. chipolana 

 of the same size. 



Length 17.4, alt. 16.4, semidiameter 5.7 mm. 



Type No. 2777, A. N.S. P. 



We have compared this with a long series of C. chipolana from the 

 type locality, and have no doubt of its distinctness, though there is 

 a general similarity. 

 Chione socia n. sp. 



The shell resembles C. woodwardi Guppy in size and shape, as 

 well as in the lunule, over which the concentric lamellae run. It 

 differs by the radial sculpture. In C. woodwardi the radial ribs run 

 to the basal border, gradually enlarging. In C. socia these ribs, 

 at first similar, soon become smaller, low and slender, and towards 

 the margin they split, so that there are very many more, and smaller 

 riljs. Crenulations of the internal basal margin are smaller and 

 twinned. 



Length 21, alt. 19, diam. 14 mm. 



Type No. 2778, A. N. S. P. 



This form shows a particular sculpture not found in the common 

 C. woodwardi of the Bowden bed, which appears not to occur in 

 Santo Domingo. In C. safitodomingensis the concentric lamellae 

 are much more widely spaced. 

 Chione primigenia n. sp. 



Related to C. cancellata and C. chipolana. The radial sculpture 

 is coarser than in chipolana, the beaks are nearer the anterior end, 

 and the tooth-plate is decidedly broader. The posterior end is more 

 prolonged and cuneate than in C. cancellata, the concentric ribs are 

 more delicate, the lunule far wider than cancellata of equal size and 

 the beaks more anterior. 



