335 Dominican Fossils — Maury 171 



hinge to the posterior angle. The sculpture of this species is 

 more elegant, the undivided ribs, which number twenty-eight, 

 have more of a tendency to be rounded at the top; in two valves 

 which belong together the ribs of the left valve are rounded on 

 the center of the shell, while on the right valve they are square- 

 topped and less ornamented ; this difference tends to occur also in 

 A. Margaretce and gicayubinica, but is more marked in riogura- 

 bonica. Length 40, altitude 25, diameter 26 mm. 



A complete series may prove this a mutation of A. guayu- 

 binica characteristic of the Rio Gurabo. 



Locality. — (Exp'd '16) Zones A and B, Rio Gurabo at Los 

 Ouemados. 



Scapharca incequilateralis, Guppy 



Plate 30, Figure 8 



* Area incequilateralis Guppy, Quart. Jour. Geol. Soc, London, vol. 32, 



p. 293, pi. 18, fig. 2, 1866. 

 Scapharca {Scapharca) inequil 'ateralis Dall, Trans. Wagner Inst. Sci., 



vol. 3, pt. 4, p. 647, 1898. 

 Area inequilaieralis Sheldon, Palaeont, Amer., vol. 1, p. 50, 1917. 



A comparison of our specimens from the Guayubin to Mao 

 road, Rio Cana, with A. latidentata Dall from the Chipolan beds, 

 Florida, shows that Dr. Dall's remarks are very fitting. A. in- 

 cequilateralis can be distinguished from its Floridian analogue by 

 the shorter, more delicate and much more numerous hinge teeth, 

 less inflated form, and more elegant sculpture. Length 29, alti- 

 tude 15, semidiameter 6 mm. This pretty, delicate Area occurs 

 at Bowden but has never before been found in Santo Domingo. 



We have a number of specimens from the Gurabo and Cana 

 Rios which apparently belong to this species, but are uniformly 

 more solid and inflated. A large valve measures 29 in length, 15 

 in altitude, semidiameter 7 mm. 



Localities. — (Exp'd '16) Guayubin to Mao road, Rio Cana; 

 Zone I, Rio Cana at Caimito; Zone G, Rio Gurabo at Los Que- 

 mados. 



