260 Guppy — Tertiaries of Trinidad. 
I have been led, by a consideration of the above facts, to enquire 
whether the refrigeration caused by the extension of glacial action 
southwards during the Newer Pliocene Period may not have affected 
lands situated so far south and so near the equator as Trinidad. 
And it must be confessed, considering the general aspect of the 
organic remains from the Matura beds, their small size, and the 
probable contemporaneity of the period of their deposition with the 
Glacial Epoch in Europe and North America, that there is some 
likelihood that glacial influences had a share in the modification 
of this fauna. ‘The influence of climate seems to show itself in the 
numerical preponderance of individuals belonging to species of Arctic 
or Northern types, and in the diminutive size generally of the 
Shells, rather than in the presence of Arctic species. 
§ 5. Relations with other Trinidad Deposits.—Several of the 
species found in the Matura beds are identical with those occurring 
in the Tamanaseries; and there are also specific affinities with the 
other Tertiaries of the Island, as mentioned in § 2. But it does not 
seem, from the lists* given by the Geological Survey, that there is 
anywhere, as far as has been discovered, the same assemblage of 
species. ‘The number of recent forms in the beds under considera- 
tion forbids us, however, to assign an older date than the ‘upper 
part of the Newer Parian’ to them: and, further, the shells from 
the deposits described in the Geological Report do not possess that 
general feature of diminutiveness which is so remarkable in the 
Matura fossils. The Ark found so abundantly in most of the Ter- 
tiary deposits of this Island (Arca incongrua of the Geological 
Survey) seems to be absent from the Matura beds. Further re- 
searches will be required to show how far some of the species of 
Arctic types now existing in the West Indian seas may have com- 
menced their existence in the tropics, from the date of the supposed 
glacial influences. 
There is a ferruginous conglomerate at Saline Bay, some little 
distance north of the exposed part of the Matura deposits, which 
may possibly belong to the same period as the latter; but it seems 
to be unfossiliferous. 
§ 6. Concluding Remarks.—The facts relative to the Matura de- 
posits may be of great interest and importance, when our knowledge 
shall have been far enough advanced to enable us to pronounce with 
some degree of certainty on the physical changes of this part of 
South America in late geological epochs. There is a great deal to 
be done in this respect. Before any set of conclusions can be esta- 
blished firmly, the observations on which they have been founded 
must be confirmed by prolonged investigation. There is, however, 
an interest of its own attaching to the explorations of our Later 
Tertiaries; and with regard to the Matura deposit, I may quote the 
very apposite remark of Mr. James Smith, of Jordanhill,—‘ As it be- 
longs to one of the first steps in the descending series, every circum- 
* Report on the Geology of Trinidad, pp. 163-6. 
