GUPPY — DOMINICA. 
389 
It appears to me highly probable ".that this break may 
be accounted for by the following hypothesis. 
Previously to the miocene period there was a much 
greater extent of land in the Caribean area than at pre- 
sent. This land was gradually submerged during the 
miocene period, and on the sinking land were formed the 
coral reefs with the associated shell-beds of that period. 
It would seem, that in this interval, nearly the whole of 
the West Indian chain was submerged. The sinking hav- 
ing proceeded to a certain point, volcanic action was deve- 
loped in immense force. The volcanoes may have con- 
tinued in activity for a very long time, during which the 
upheaval occurred, which put an end to the miocene 
period, and exposed the beds which had been formed. The 
seas probably became unfitted for the existence of many 
of the coral reef loving molluska of the miocene period, 
which became extinct. Their living analogues are now to 
bo found in the eastern seas, whither their ancestors pro- 
bably migrated during the earlier tertiary period, when 
perhaps the submergence of the Atlantis had left a chain 
of coral Islands in the ocean between meridional America 
and North Africa. 
Upon the shores of the land now upheaved there was a 
renewal of coral growth ; but the corals were, in few in- 
stances, identical with those of the former period, and they 
belong, with slight variation, to the existing coral fauna. 
There may have been at this time a comparative cessation 
of volcanic activity, during which, the old volcanic mate- 
rials were formed by the waves and streams into a con- 
glomerate. But a new outburst seems to have succeeded, 
during which the land was again elevated to the extent of 
200-300 feet. This elevation was probably a slow process, 
and it may have extended into the historical period j for 
