16 



AXXALS XEW YORK ACADEMY OF SCIEXGES 



This type of topography is represented by the small level tract surrounded 

 or dotted over with small hills, called "pepino hills" locally, standing- 

 like haystacks above the plain at many dilt'erent elevations above the sea. 

 This leads to the belief that the fundamental control in its development 

 is the j)resence of a shaly bed in the series, Tvliich forms at each point the 

 basis of the local j^lain. The hillocks standing above it or surroimding 

 it represent remnants of the more massive and jDrobably more porous and 

 more easily destroyed limestone which has been attacked and largely 

 removed by weathering, and especially by solution, down to the more 



Fig. 3. — L nconformiti/ lelo>r tlu: Aieviho f>.riiiati<.u 



This view shows the older tilted and eroded tvifiEs and shales l)elow, as seen on the 

 Arecibo River. The contact is immediately beneath the horizontally bedded limestones at 

 about the center of the view vs-here the chief weathering is noted. 



resistant shaly soil-forming member. If this is the principal cause of 

 the peculiar topographic form just described, it is quite easy to see that 

 the distribution of such features should be expected to be rather irregular 

 both in lateral extent and in actual elevation above sea level or in rela- 

 tion to the different horizons in the formation itself. In regarding this 

 as the principal factor, there is no tendency to overlook the fact that the 

 island has stood at different elevations with respect to sea level in former 

 times, and that a corresponding difference in ground water levels would 

 be felt tbrouo'hont the border reaion. But there is no evidence whatever 



