347 Dominican Fossils — Maury 183 



fold so that the valves interlock as shown in the figure. The 

 hinge is remarkable for the presence of two equal and equidistant 

 pits on either side of the ligament pit. This condition may be 

 pathological but, as shown by the figure of the interior, it sug- 

 gests the multiple pits of Gcrvillia and Perna. Length no, alti- 

 tude i2o, diameter 60 mm. 



Of the Ostreas in the Cornell collections this species most re- 

 sembles O. sellceformis Conrad but that species is broad at 

 the hinge while ours is narrow and sloping. The peculiar sad- 

 dle-like undulations are, however, like those of the Eocene 

 species. Our shell is named in honor of Professor Harris, with- 

 out whose encouragement and most effective aid on all sides, this 

 work would never have been done. 



Locality. — (Exp'd '16) Bluffs of Rio Gurabo. 



Ostrea megodon Hanley 



Plate 34, Figure 3 



Ostrea megodon Hanley, Proc. Zool. Soc. London, p. 106, 1845. 



Cf. Ostrea cerrosensis Gabb, Geol. Surv. California, vol. 2, p. 35, pi. 



11, fig. 61, 1869. 

 Ostrea megodon Dall, Trans. Wagner Inst. Sci., vol. 3, pt. 4, p. 685, 



189S; pt. 6, p. 1586, 1903. 



A striking species, sickle-shaped, with four or five large, 

 marginal, tooth-like folds. Adult attached by the apex only, as 

 one of our shells clearly shows. 



This species was founded on a recent shell from Peru in 

 Cuming's collection. Gabb described a very similar shell from the 

 Californian Post-Pliocene as O. cerrosensis, which Dall united with 

 megodon. It is a curious and interesting fact that the two species 

 megodon and haitensis (or their descendants) should be found in 

 the Santo Domingo and Bowden beds and on Cerros Islands off 

 the Californian coast. It recalls the case of Venericardia plani- 

 costa, long extinct on the East coast but with the descendants of 

 migrants still living on the West Coast. O. megodon is now re- 

 ported for the first time from the Dominican blue clays. 



