46 
PROCEEDIN' GS OF THE SCIENTIFICT ASSOCIATION'. 
of these rocks with the tertiaries of Trinidad. The tertia- 
ries of Trinidad were divisible into three groups : the Plio- 
cene, of which the speaker had on a former occasion given 
an account to the Association : the Upper Miocene, contain- 
ing the tertiary coal-beds, the greatest development of as- 
phalt, and an abundance of gypsum in the form of sele- 
nite ; and lastly, the beds designated by the speaker as 
Lower Miocene 1 , but which may very probably have to be 
classified as Eocene. Now the newest fossiliferous strata 
in Trinidad, the Pliocene before mentioned, contain a few 
extinct species some of which have been found in the Miocene* 
of San Domingo and Jamaica, and are therefore probably 
older than tho Coral formation of Barbados in which 
all the' Shells and Corals are of existing species. The 
older of the two formations of Barbados (the Scotland forma- 
tion) had yielded between three and four hundred species 
of minute siliceous organisms which had been described by 
Ehrenberg, but which afforded no clue to the age of the de- 
posit because no similar organisms had ever been found 
elsewhere. Sir Pobert Schomburgk had found some shells 
in an isolated rock or boulder in the Scotland formation, 
and the only three identifiable species were described by 
Professor Eorbos. The speaker had recently discovered 
one of these shells, a JVucula of a peculiar type, allied to 
iV. divaricata Of the Pacific, and to XT. Colboldicc of tho En- 
glish Crag, in the lower Miocene beds of San Pernando. 
Therefore ho presumed that the Scotland formation was 
newer than the lower Miocene of Trinidad, the boulder in 
which the fossils were found having probably been deriyed 
from a pre-existing rock of that age. Then as far as the mi- 
neralogical eyidence goes it is unquestionably in favor of the 
correlation of these petroleum-bearing rocks of Barbados 
with the uppor Miocono of Trinidad, which they resemble in 
