GEOLOGY AND GEOLOGIC HISTORY. 59 



the Eocene has not been proved. The Eocene limestone of the Dominican 

 Republic is probably not so thick. 



On the lower slopes of the front range of the Cordillera Septentrional 

 near Damajagua, in Santiago Province, there is hard light-gray limestone 

 of Eocene age. Some of this rock contains inclusions of hard, brittle, 

 banded calcareous argillite, which breaks with rectangular, smooth faces 

 and was probably derived from the Cretaceous rocks that are believed to 

 underlie the Eocene at this locality. In a fragment of the Eocene limestone 

 picked up loose on the hillside, but evidently not far from place, Doctor 

 Cushman identified the species of Foraminifera listed on page 105 as from 

 station 8721. Rock in place near this locality contains identifiable Fora- 

 minifera, which are listed on page 105 (stations 8725 and 8725a), but they 

 are neither so well preserved nor so abundant as the species at station 

 8721. 



Limestone of Eocene age also outcrops at several places near Altamira, in 

 the Province of Puerto Plata. The identifiable Eocene fossils collected in 

 Santiago and Puerto Plata provinces are listed on page 105. 



Besides the rocks in Puerto Plata Province that have been identified as of 

 Eocene age, Eocene strata probably occur near the city of Puerto Plata. 

 South of Rio San Marcos, along both the railroad and the trail to Baja- 

 bonico, the oldest rock examined in exposures was serpentine, above which 

 is limestone that contains angular fragments of lava. The corals, probably 

 Oligocene, from the north slope of Monte Isabel de Torres (station 8675), 

 listed on page 111, came from a younger geologic formation. The limestone 

 above mentioned would therefore be either of Upper Cretaceous or Eocene 

 age, probably Eocene, but further study is needed before a positive opinion 

 will be warranted. 



The caves of Las Guacaras are in thick, massive, dark blue-gray siliceous 

 limestone, so hard that it strikes fire with steel. This limestone forms 

 many steep hills, some of them 100 meters high, in the Sierra Prieta west 

 of Rio Yuna and south of the road from La Vega to Cotui. (See PI. VII, B.) 

 The rock is so massive that it is difficult to ascertain its strike and dip. At 

 El Comedero, one of the caves, the strike appears to be east, the dip 

 70° S. Some of these scattered limestone hills appear to be fault blocks. 

 No fossils were obtained from this limestone, but the stratigraphic and 

 structural relations indicate that it is of Eocene age. 



Blue limestone similar to that at the caves of Las Guacaras is exposed in a 

 small arroyo crossed by the road from La Vega to Cotui several kilometers 

 west of Rio Yuna. 



In the vicinity of Hatillo, a village near Rio Yuna on the road from Cotui 

 to Piedra Blanca, there are several hills composed of hard limestone, which 

 is in part dark blue and somewhat bituminous and in part cream-white. 

 The rock strikes N. 10° W. and dips 25° to 30° S. At one locality large 



