OF SANTO DOMINGO. 



151 



The Samba hills, endmg castwardly in the loma Caracoles and loma Seboriico, are 

 a low range, in part isolated from the main chain, and lie midway between its foot- 

 hills and the river. They are made np entirely of Tertiary rocks, and afford some 

 excellent sections for study. The last-named are low and are separated from the 

 foot-hills only by narrow canons. The road runs along the north base of the latter, 

 and shows it capped with white limestone and calcareous limestone, dipping north at 

 low angles, and abounding in corals of the massive forms. Very few mollusca were 

 discovered in this vicinity. The soil between the hills and the river is a black mud, 

 similar to that found opposite, at Ponton, and resembling that of the vicinity of 

 Moca. Along the entire northern face of these hills, east of the Mao River, corals, 

 more especially of the more solid kinds, ai'e strewn over the surface or project from 

 the decomposing rocks. Usually they are so weathered as to show no distinctive 

 characters ; but occasionally, especially where the matrix has been moderately soft, they 

 are as well preserved and the surfaces as sharp as recent specimens. A great mass of 

 Meandrina before me, picked up by myself, weathered out thus on the top of the 

 ground, is as perfect as pieces I have fished up on the coast. The Amina River cuts 

 through the range between these two hills, and exposes a bluff of blue shale, rich in 

 fossils, dipping, as is always the case in these hills, at a low angle north. The strike, 

 if such can be said to exist, with a dip never exceeding 10°, is strictly coincident 

 everywhere with the direction of the hills, while the dip is equally constant towards 

 the valley. At this point the Tertiary is seriously encroached on by the Cretaceous 

 rocks which extend northward, their upturned edges being but thinly covered by the 

 later formation. On the Guanajuma the two formations are in contact, but a few 

 hundred yards south of the road that crosses at Bohie Viejo. The slates of the 

 Sierra strike due east and west and dip south fi'om (35° to 70°, while the nearly 

 horizontal Miocene, here represented by the gravel beds of the Mao, overlie them at 

 various levels. I found some little patches of this gravel a quarter of a mile south 

 of the boundary, filling depressions but a few rods across. 



Although the limestones continue for a little further west on the outer face of the 

 range, they thin out gradually, and south of the Samba Hills they are represented 

 by beds of gravel which bear the same relation to them that the Azua gravels bear 

 to the coast limestone. In the hills covered with grass and guano-palm, over which 

 the road runs between Bohio Yiejo and the settlements on the Mao, these gravels 

 first come in as an important matter of the formation ; and here they consist of beds 

 of coarse gravel, alternating with strata of coarse and fine sandstone, and a peculiai", 

 very soft, earthy shale. This latter rock is especitilly well developed towards the 



