A. J. Jukes-Browne—Foraminiferal Limestones. 271 
ground mass of fine material, full of rounded bodies which can be 
identified as Globigerine. All are much altered and are filled with 
calcite, but in many of them the cell walls can be clearly distin- 
guished; others are so blurred and calcified that unless some were 
better preserved they would hardly be recognisable. There are also 
many smaller blebs of calcite which may represent the single 
spheroidal cells so often found in Chalk and in Globigerina ooze. 
No other mineral but calcite is discernable, and the rock may be 
regarded as a fine-grained Globigerina ooze which has undergone 
partial marmarosis. 
A third specimen is a compact and crystalline grey limestone, in 
which many minute specks of iron-pyrites can be distinguished with 
tbe unaided eye. Under the microscope it is seen to contain a much 
greater variety of ingredients than the limestone above described. 
Globigerine are very numerous and in a better state of preservation, 
the cell-walls being quite clear and distinct, but with them are some 
larger Foraminifera, chiefly Amphistegine, and a few which appear 
to be small Nummulites, and one or two nautiloid forms. There are 
also many fragments of a clear yellowish mineral which appears to 
be glauconite; but differs somewhat from the green glauconite of 
our own Cretaceous rocks. The grains are of irregular and often 
angular shapes and some of them seem to be entangled with crystals 
of calcite ; such grains polarize in patches which change from yellow 
to dark-grey, while parts remain clear and yellow, as if the original 
mineral had undergone some partial kind of alteration. As, however, 
the same yellowish mineral is seen filling some of the Globigerine, 
I think it may be regarded as glauconite, and Mr. J. J. H. Teall, 
F.R.S., to whom a slide was submitted, concurs in this opinion. 
Scattered through the slide are many very small cubical crystals 
of an opaque mineral, which is evidently the iron-pyrites visible in 
a hand-specimen. 
The fourth sample is also a compact crystalline grey limestone, 
similar in general aspect, but without any pyrites. Under the micro- 
scope further differences are apparent; there are no Globigerine, 
the rock being chiefly made up of Amphistegine and Nummulites,* 
with a few others which resemble Cristellaria in section and some 
fragments of shell. Mingled with them are grains and patches of 
a yellowish glauconitic mineral occurring in the same way as in the 
specimen just described. There seems to have been a little greyish 
mud between the Foraminifera, but it does not occupy so much of 
the field as the latter do, and the interstices are filled up with 
crystalline calcite. 
The interest of these limestones is (1) their occurrence in the 
Grenadine group, which was supposed to consist entirely of igneous 
rocks, and (2) their similarity to rocks which occur in Trinidad 
and Barbados. Barbados lies about 120 miles to the H.NE. of 
Canouan, and San Fernando, in Trinidad, is about 170 miles away 
to the southward. 
1 For the identification of these genera in the slide, I am indebted to Dr. G. J. 
Hinde, F.G.8. 
