20 
Bulletin 35 
168 
Page 40 
4^.— Climate of the period of deposition. 
Bearing in mind what has been said respecting the 
l^roportion of recent and extinct species, it will appear 
that these deposits probabh' belong to an epoch not 
far removed from that of the glacial and ])reglacial 
beds of Europe. 
But the extremely small size of the fossils found at 
Matura is one of the most remarkable features of the 
deposit. Even where the shells belong to recent types 
of average size, the fos.sil representatives are almo.st 
invariabh' dwarfed. There are only one or two excep- 
tions to this rule, e. g. Cardium isocardium, Turritella 
imbricata and Bulla striata, which attain an ordinarj- 
but not a large growth . 
When the fos.sils belong to recent types of small 
.size and arctic genera, they are not smaller than their 
living repre.sentatives. As examples of this, I may cite 
Astarte (Gouldia) martinicensis, the CorbnleB, \.\\^ Leda, 
and the Nucula-. 
I have been led from a consideration of the above 
facts to enquire whether the refrigeration cau-sed 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 mu.st be confe.ssed, con.sidering the general aspect of 
the organic remains from the Matura beds, their small 
size, and the probable coatemporaueity of the period of 
their de])o.sition with the glacial epoch in Europe and 
North America, that there is .some likeliho.od that gla- 
cial influences had a .share in the modification of the 
fauna of the Matura beds. The influence of climate 
seems to show itself in the numerical preiionderance 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. — Relatio7ts with other Deposits. 
Several of the species found in the Matura beds are 
identical with those occurring in the Tamana .series. 
