94 GEOLOGICAL RECONNAISSANCE OF THE DOMINICAN REPUBLIC. 



the biologic. In some cases it was possible to apply both diastrophic and 

 biologic criteria, as, for instance, in referring the Baitoa formation to the 

 Miocene. The underlying Tabera formation, which, as is clearly shown by its 

 fossils, is of the same or nearly the same age as the middle Oligocene Antigua 

 formation, was folded and eroded before the Baitoa was deposited upon it. 

 It may reasonably be inferred that this folding and erosion consumed a long 

 time — probably all of upper Oligocene time — and that the Baitoa formation 

 is of Miocene age. Moreover, the fauna of the Baitoa shows affinities with 

 that of the other members of the Yaque group, not with the faunas of the 

 older formations. The Baitoa is therefore referred to a stratigraphic position 

 low in the Miocene. One result of this conclusion is to place in the 

 Miocene the type species of the genus Orthaulax, 0. inornatus Gabb, a 

 species that had been supposed to be of Oligocene age. 



RELATIONS OF DOMINICAN TERTIARY AND QUATERNARY BIOTA. 



Within the last two years Vaughan has discussed in three papers the 

 relations of the West Indian and Central American Tertiary marine inver- 

 tebrate fauna, 1 and Dr. C. J. Maury 2 and Dr. Bela Hubbard 3 have more 

 recently published two papers that are devoted particularly to Porto Rico. 

 As rather full references to other literature are given in the papers cited, 

 particularly the longer one by Vaughan, the present discussion is much 

 condensed. 



EOCENE. 



The Dominican Eocene seems to be of very nearly the same if not the 

 same geologic horizon on both the north and the south side of the island. 

 The tables on pages 105-106 show that the same species are found on both. 

 The same or a very similar fauna is found in Saint Bartholomew, Jamaica, 

 Cuba, Nicaragua, Costa Rica, and Panama, and probably in Colombia and 

 Trinidad. Vaughan also obtained it in Haiti at Cape Hai'tien and between 

 Plaisance and Ennery, at an altitude of about 705 meters above sea level, 

 on the north side of the summit of Mount Puilboreau. The genera of 

 Foraminifera in the Haitian deposits were determined by Doctor Cushman 

 as Globigerina, Calcarina, Orthophragmina, Conulites, Biloculina, and Quin- 

 queloculina. To the Eocene limestone that is so well exposed in north- 

 western Haiti Vaughan has applied the name Plaisance limestone. 



This fauna is late Eocene, the same age as that of the Jackson formation 

 and Ocala limestone of the southern and southeastern United States and 



'Vaughan, T. W., Correlation of the Tertiary geologic formations of the southeastern United States, 

 Central America, and the West Indies: Washington Acad. Sci. Jour., vol. 8, pp. 268-276, 1918. Geologic 

 history of C'entral America and the West Indies during Cenozoic time: Geol. Soc. America Bull., vo). 29, 

 pp. 615-630, 1919. The biologic character and geologic correlation of the sedimentary formations of 

 Panama in their relation to the geologic history of Central America and the West Indies: U. S. Nat. Mus. 

 Bull. 103, pp. 547-612, 1919. 



! Maury, Carlotta J., On the correlation of Porto Rican Tertiary formations with other Antillean and 

 mainland horizons: Am. Jour. Sci., vol. 48, pp. 209-215, 1919. 

 4 Hubbard, Bela, The Tertiary formations of Porto Rico: Science, n. s., vol. 51, pp. 395, 396, 1920. 



