171 Dominican Fossils — Maury 



small arroyo runs from it into the Rio Gurabo. The amphithe- 

 ater is no doubt a singular form resulting from erosion. 



The Gurabo was then forded three times to observe the 

 striking bluffs of blue clay about 100 feet high, with a charac- 

 teristic concave curve. These are Gabb's "blue shales" really a 

 hard clay not sufficiently consolidated for shales, nor are they 

 laminated. They contain wonderfully preserved gastropods and 

 more fragile pelecypods, among them the large Spondylus. Here 

 and elsewhere in the Yaqui Valley this proved a very character- 

 istic fossil. 



Three days and a half were spent in this region on the east 

 bank of the Gurabo collecting. The best accomodations obtain- 

 able at night were native cots in the combined chicken coop and 

 store house at the pulperia of Los Quemados ( 12 on sketch map). 



Trips up and down the river on foot were made, going as 

 far as possible. It was impossible to ride, as there are no trails 

 for horses. 



Above Los Quemados the river cuts through limestone al- 

 ternating with blue clays. The limestone tumbles in great 

 blocks into the river and down its banks, and one has to crawl 

 under or over these great blocks. The Gurabo river here is 

 twenty-five to thirty-five feet wide. Its bed is of clay with 

 gravels and bowlders from the Cordillera, the bowlders being of 

 both metamorphic and igneous rocks. The sides are precipious, 

 and 80 to 100 feet high. They are usually more sloping where 

 the limestone formation is present except where it forms a pro- 

 tective cap. The plain of the river bottom is usually cultivated 

 and is up to forty rods wide. One of the very characteristic 

 trees on the banks is the Mara, which is' magnolia-like. Abound- 

 ing in the trees and bushes of the banks is a green snake, the Ctc- 

 lebra verde (Uromacer catesbyi), which is peculiar to the island. 

 This species is used for the Voodoo worship in Haiti. 



The party left Los Quemados for Mao, by good fortune via 

 Cercado (13 on the map and shown on frontispiece). This is 

 one of Heneken's localities and it gave us a splendid yield of fos- 



