78 



Bulletin 35 



226 



Page 105 



{see diagram, Fig. 2). Plain evidences of this remarkable 

 subsidence are to be found in the submerged valleys about 

 the Bocas, — valleys obviously produced by subserial denuda- 

 tion, but now sunk below the level of the sea. Not less 

 clear is the testimony of the wide and comparatively shallow 

 valleys of Carenage and Diegomartin, originally much deeper, 

 but now to a great extent filled up by alluvium. As we go 

 eastward from Diegomartin the valleys become steeper and 

 narrower, assuming the form of mere ditches in their lower 

 portions, but having immense delta-like deposits of alluvium 

 at their mouths, ranging from 80 to 200 feet in height above 

 the level of the Caroni plain. These moraine-like deltas are 

 evidences of upheaval rather than of subsidence ; they are 

 not found in the valleys west of Portofspain, but, beginning 

 with the Santacruz valley, they increase in magnitude as we 

 go east. 



I have already said that the petrological and physical fea- 

 tures of the Caribean group would lead us to assign a high 

 antiquity to it ; but the absence of fossils has prevented any 

 precise determination of its age. I shall presently indicate 

 what evidence we have gained on this head, since the 

 publication of the Geological Report on Trinidad. 



2. dossils of the Caribean Group. 



In 1869 I had communicated to the Geological Society of 

 London my discovery of organic remains in the Caribean 

 Series of Trinidad. I described to that Society a piece of 

 limestone which exhibited unmistakeable marks of organic 

 origin. The specimen in question was apart of an irregular 

 string of limestone, found on digging a trench in the decom- 

 posed micaslate in the San Francois valley, north of the 



