FOSSIL FORAMINIFERA FROM THE WEST INDIES. 25 



SANTO DOMINGO. 



The collection containing fossil Foraminifera from Santo Domingo 

 was placed in my hands for study in connection with the work of Dr. 

 T. W. Vaughan on other groups of the same material. The collection 

 is that of Dr. Carlotta J. Maury of Cornell University, and represents 

 several horizons and different localities. Only those localities at which 

 Foraminifera were found are mentioned here. 



Three localities with the following data have furnished the Foramin- 

 ifera: Zone A, Rio Gurabo; Zone G, Rio Gurabo ; Zone H, Rio Cana ; 

 Zone I, Rio Cana; Bluff 2, Cercado de Mao;Bluff3,CercadodeMao. 



In all, these localities have yielded 33 species of Foraminifera. As 

 is usual in such material, a few species dominate while the others are 

 obtained only after long and diligent search of the finer material and 

 are too often represented by single specimens. For this reason the 

 occasional scattered records of one species present in one locality and 

 not in another when the general assemblage in the two is very much 

 alike may mean that there are certain uniques which, if the search 

 could be prolonged indefinitely, would be represented in the similar 

 lot of material from which it now appears to be absent. Such an 

 explanation is probably sufficient for most of the records of this sort 

 in Zones H and I and Bluffs 2 and 3. It explains probably the two 

 species of Polystomella which are represented at single localities by 

 single specimens, while the third species is common and represented 

 at all four of the stations. It does not account for the Orbitolites, 

 however, which is almost if not quite the most abundant genus in the 

 Bluff 3 material and is lacking in the others. This again may be 

 accounted for in the possible slight difference in ecologic conditions. 

 In the tropics especially, Orbitolites is very apt to occur in great num- 

 bers under certain conditions. For example, about Montego Bay, 

 Jamaica, Orbitolites is met with occasionally or even frequently in 

 dredgings of several fathoms in the sand among the reefs, but about the 

 Bogue Islands to the west of the bay, in a few inches of water, Orbito- 

 lites becomes very abundant. The short Posidonia to which the young 

 of Orbitolites attach themselves is here abundant in the comparatively 

 quiet waters and the specimens of Orbitolites make up a large part of 

 the deposit about the roots of Posidonia. Some such conditions prob- 

 ably explain the very great abundance of Orbitolites and of Asteri- 

 gerina and Amphistegina in certain of the other localities. 



The geological sequence seems to present three phases at least. Zone 

 A is the youngest and is represented by but 2 species in the rather 

 limited material at hand. Both of these species occur living at the 

 present time and the bed containing the fossils can not be of any but 

 late Tertiary age. 



Zone G is represented by a single species in considerable numbers 

 unlike anything in the other beds, but generically like those of the 

 lower members. Its age from this seems to be Miocene. 



