327 Dominican Fossils — Maury 163 



the radials. Ligament pit small, triangular, dividing the teeth 

 into an anterior and posterior series; teeth irregular, the anterior 

 nearly vertical, posterior very oblique. Length 7, altitude ap- 

 proximately 7 mm. A rare and exquisite little shell. 



Locality. — (Exp'd '16) Between Hato Viejo and Potrero, 

 Rio Amina. 



Genus Arca Linne 



Dr. Pearl Sheldon, whose fine Monograph on Atlantic Slope 

 Areas has lately appeared, has very kindly examined our Santo 

 Domingo Arks, and discriminated most carefully between the 

 species, the majority of which are new. Her expert and inti- 

 mate knowledge of the genus gives to these discriminations a high 

 value. 



Arca occidentalis Philippi 

 Plate 29, Figure 3 



Arca occidentalis Philippi, Abbild. u. Beschr., 3, p. 14, pi. 17b, fig. 



4a-c, 1847. 

 Arca noce Guppy, Quart. Jour. Geol. Soc. London, vol. 22, p. 293, 1866. 

 Arca occidentalis Guppy, Id., vol. 32, p. 531, 1876. 

 Arca occidentalis Sheldon, Palseont. Amer., vol. 1, p. 8, pi. 1, figs. 



8-1 1, 1916. 



Our fossils from the bluffs seem identical in every respect 

 with recent shells of this species from the Monte Cristi beach. 

 The species has been reported from Bowden, and is widespread 

 in the Pleistocene and recent Antillean faunas. 



Localities. — (Exp'd '16) Zone D, Rio Gurabo at Los Que- 

 mados; Zone H, Rio Cana at Caimito. 



Arca umbonata Lamarck 



Plate 30, Figure 1 1 



Arca umbonata Lamarck, An. s. Vert., vol. 6, p. 37, 1819. 

 Arca imbricata Gabb (in part), Trans. Amer. Phil. Soc, vol. 15, p. 

 254, 1873. 



