78 
Bulletin 35 
226 
Page 103 
(see diagram, Fig. 2). Plain evidences of this remarkable 
subsidence are to be found in the submerged valleys about 
the Bocas, — valle3’s obviousl}* produced b}" subaerial denuda- 
tion, but now sunk below the level of the sea. Not le.ss 
clear is the testimoii}' of the wide and comparatively shallow 
valle\-sof Carenageand Diegomartin, originalh^ much deeper, 
but now to a great extent filled up bj" alluvium. As we go 
eastward from Diegomartin the valle\'s 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 ; thej' are 
not found in the valle3"S west of Portofspain, but, beginning 
with the Santacruz valle3% the3" increase in magnitude as we 
go east. 
I have alread3' said that the petrological and ph3-sical fea- 
tures of the Caribean group would lead us to assign a high 
antiquit3" to it ; but the absence of fossils has prevented an3' 
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. .Posstls of the Caribean Group. 
In 1869 I had communicated to the Geological Societ3’ of 
London my discover3" of organic remains in the Caribean 
Series of Trinidad. I described to that Societ3' 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 micaslate in the San Francois valle3q north of the 
