369 Dominican Fossils — Maury 205 



over an extremely small but impressed lunule only about one 

 millimeter in length ; anterior dorsal area narrow, marked by 

 two weak sulci ; po sterior area long, undulated, defined by a 

 very sharp, narrow sulcus ; surface of shell marked by very fine, 

 close, concentric strise and traces of faint, just perceptible, obso- 

 lete radial lines ; teeth strong, normal. Length of left valve 45, 

 altitude 50, semidiameter 6 mm 



This species is apparently the ancestor of M. caloosaensis 

 Dall, from the Florida Pliocene and M. Childreni Gray (type of 

 the subgenus) living in the Gulf of California. Our shell can 

 readily be differentiated from caloosaensis by the posterior dorsal 

 area. In the Pliocene shell the area has two very sharp sulci, — 

 one limiting, one central ; while in our shell the central sulcus is 

 represented by a broad undulation. 



This is the first Miltha found in the Dominican blue clays. 

 Though well represented in the Eocene the stock dwindled and 

 there are but two living species, one, as noted above, on the Cal- 

 ifornian coast, the other off Mozambique. 



I take great pleasure in naming this rare shell in honor of 

 Dr. Smith Woodward of the British Museum, as a token of ap- 

 preciation of many kindnesses. 



Locality. — (Exp'd '16) Bluff 2, Cercado de Mao. 



Phacoides {Miltha) riocanensis, n. sp. 

 Plate 35, Figure 7 



Shell sub-orbicular, disciform ; beak nearly central ; entire 

 surface ornamented with concentric lamellae closely set on the 

 umbo but becoming progressively more distant distally ; between 

 the lamellae are weak, irregular, concentric stirae. Length 48, 

 altitude 48, semidiameter of right valve 7 mm. 



This is a representative of the type of Milthas with sharp, 

 concentric lamellation, exemplified by M. hillsboroensis- and disci- 

 formis Heilprin, from the Pliocene of Florida. Our shell is closer 

 to the former species, but differs markedly in its fewer concentric 

 lamellae which become more and more distant as the shell becomes 

 adult. The interior of our shell is concealed by a hard matrix, but 



