317 
Guppy Reprint 
169 
So much b)" wa}’ of introduction. I will now turn to the 
subject I have to bring before you toda}'. 
In order more easily to recall to your minds the relative 
position in the earth’s crusts of the strata developed in this part of 
the w'orld, I have here a rough diagram in which the strata I am 
referring to are distinguished bj" colours while those which are not 
Page 25 
represented here are left uncoloured. On this diagram I have 
shown our oldest strata, those of the northern hills, as being be- 
tween the carboniferous and devonian. This is a sort of com- 
promise to represent the uncertaint)- of our knowledge of the ex- 
act age of these formations, for up to the present time we have 
failed to find any v’ery satisfactory evidence of their age. The 
geological surveyors of 1859 nowhere distinctly state an age for 
these formations, but it may be inferred from what the}" say in 
the geological report and from what Wall says in his paper on 
Venezuela that they were inclined to consider that they are of 
paleozoic age. Until now I have so treated them. My friend, 
the late Ralph Tate, Professor of Geology in the University of 
Adelaide, thought that they might be jurasic. I infer from what 
Mr. Cunningham Craig says about them that he leans to a cre- 
taceous age for these rocks. On looking over the evidence, how- 
ever, I cannot think that they are younger than carboniferous. 
The only paleontological evidence is that found by me, except a 
Rhynconela mentioned by Mr. Cunningham Craig w’hich I have 
not seen. But that brachiopod genus ranges from the Silurian to 
the present time, .so it can hardly be said to have any decisive ef- 
fect upon the question. In a paper read by me to the Scientific 
Association of Trinidad in 1877 I gave an account of the older 
rocks of Trinidad and referred to a previous paper which I had 
communicated to the Geological Society of London on the sub- 
ject. I gave a list of the fossils I had discovered — a very .small 
list of imperfect specimens, but which, so far as it w"ent, was in 
favour of the paleozoic age of the.se rocks, as was admitted by W. 
O. Crosby of Bo.ston in reviewing my work on them. From the 
