LECHMERE GUPPY OLDER ROCKS OF TRINIDAD. 
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 andDiegomartin, 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. The Fossils 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 a part of an irregular 
string of limestone, found on digging a trench in the decom- 
posed mieaslate in the San Franqois valley, north of the 
