314 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 13, No. 14 
Porto Rico east of San Juan. As I have given in the final part of 
Bulletin 103 of the United States National Museum a rather full 
account of the distribution of marine deposits of these ages, except 
for the Virgin Islands, Porto Rico, and*the island of Haiti, I will not 
repeat what I published, except in so far as it bears on the problems 
under discussion. 
From corals collected by R. T. Hill in western Porto Rico in 1898 
IT pointed out in notes published by Hill in 1899 that his Pepino 
formation is of the same age as the Antigua formation which is now 
classified as of middle Oligocene (Rupelian) age. In addition to this 
horizon Miss Maury has recently recognized upper Oligocene and 
lower Miocene in western Porto Rico. The geologic exploration 
made for the Military Government during April, May, and June, 1919, 
in. the Dominican Republic has led to the recognition there of upper 
Eocene, middle Oligocene, upper Oligocene, and six Miocene hori- 
zons of which the lowest and the upper three are new—that is, at 
least seven definable new Tertiary horizons were recognized in the 
Dominican Republic. South of Santiago, near Baitoa, Condit and 
Cooke found the basal Miocene resting on the deformed, folded, and 
eroded surface of middle Oligocene deposits which carry the Antiguan 
foraminiferal and coral fauna. The specimens of Lepidocyclina are 
equaled in size only by those in Antigua where some are four inches 
in diameter. The Eocene formations of the Republic of Haiti have 
been briefly discussed by Woodring in two recent papers.’ Later the 
significance of these determinations will be indicated. 
Pleistocene deposits 
Although I did not land on the Cordilleras reefs, I could see from 
the subchaser on which I travelled that they are composed of lime- 
stone. A specimen of soft limestone from Icacos Key, given me by 
Mr. Jorge Byrd-Arias, is a very fine-grained oolite. I suppose that 
this rock is of Pleistocene age from analogy with Florida and the 
Bahamas. 
SUMMARY OF GEOLOGIC HISTORY 
(1) The presence of shoal water deposits of Upper Cretaceous age, 
in Saint Croix and in the islands on the Virgin Bank from Saint 
John to Porto Rico and in Porto Rico shows that the major tectonic 
axis of this part of the West Indies antedates Upper Cretaceous time, 
6 Woodring, W. P., Middle Eocene foraminifera of the genus Dictyoconus from the 
Republie of Haiti: this Journal 12: 244-247. 1922; and An outline of the results of 
a geological reconnaissance of the Republic of Haiti: Ibid. 13: 117-129. 1923. 
