THE GEOLOGIST. 
47 
overlaid by a few inches of clay, which contains many small shells, 
among which a small species of oyster ( 0. accuminata) is particularly 
prevalent. The ragstone is thirteen feet, and the very fissile slate, 
about five feet thick, immediately underlies it. The neighbourhood, 
however, of Jfauuton, Eyeford, and Temple Guiting alfords the best 
sections, and numerous quaiTies are in constant work — as many as 
120,000 slates being obtained during the season. At Northleach the 
slate becomes an oolitic freestone, mainly composed of small shells, 
more or less comminuted. This portion of the Great Oolite occupies a 
considerable extent in the eastern district of the Cotswolds, and may 
also be noticed at Notgrove, Miserden, and on the descent from Min- 
chinhampton to Brimscomb. Lithologically and zoologically it is 
identical with the slate at Stonesfield, in Oxfordshire, which has long 
been famous for its organic remains ; indeed, it may be distinctly traced, 
with few interruptions, from Sevenhampton to Stonesfield. The slate 
itself, like the Minchinhampton Oolite, is extremely valuable for archi- 
tectural purposes, and forms a good and useful building stone. The 
young geologist, however, can see far more of it in Gloucestershire, 
where many sections are exposed at the surface ; while in Oxfordshire, 
it is worked underground, and the workings are reached by means of 
a shaft. 
To the palaeontologist the Stonesfield slate is particularly interesting, 
from the abundance and variety of its fossil contents; for here we have, 
for the first time in the oolitic group, the relics of Mammalia and land 
saurians, though occurring again at a much later interval, higher up, in 
the Purbeck and Wealden at the close of the system. The Lower Oolite 
group in the Cotswold Hills contains, as we have seen, little else but 
an assemblage of marine shells, which attest the condition of the ocean 
at that epoch. The Stonesfield slate, on the other hand, affords a 
remarkable exception — for shells are not very numerous, the character- 
istic fossils being land plants, and relics of fish and saurians, terrestrial 
and marine, chiefly bones, teeth, and jaws. Parts of Insects, wing 
covers, and bodies of beetles, and wings of dragon-flies, which doubtless 
formed the prey of the insectivorous ^Mammals of the period, are not 
unfrequently associated with the above. Hitherto, no traces of Mam- 
malia have been met with in Gloucestershire, but it is by no means 
improbable that they will be hereafter detected. A few jaws only of 
small opossum-like animals of this class have been discovered in Oxford- 
