Vol. 58.] JURASSIC OF THE SOUTH WALES DIRECT LINE. 737 
thickness cannot, however, be very definitely stated. The total 
thickness of the series is approximately the same in the two shafts 
numbered 5 & 4 (that is, in the permanent shaft near the Cross 
Hands, and in the temporary one which les about 200 yards 
farther east); but the lithological character of the rocks in the 
two borings does not absolutely correspond at corresponding levels. 
The following general summary is, nevertheless, applicable equally 
to either shaft, the beds being arranged in descending order :— 
Thickness in feet. 
; Blue, yellow, and white oolite (the oolitic 
GLopata- and 
CorRALLINE BeEDs. 
25 
character asa rule strongly and uniformly 
marked). 
{ 
| 
Very fossiliferous, compact limestones, with | 
Trigonia costata and Rhynchonella 10 
spinosa. 
Coarsely granular, yellow limestone, full of | 
comminuted shells, but with no deter- 
minable fossils. ; 
Oolitic limestones of varied texture, with 
some soft sandy beds, and, at the base, ' 25 to 30 
a compact fossiliferous limestone. 
TRIGONIA-GRIT. 
Or 
The following is a complete enumeration of the different types of 
rock, belonging to the Inferior Oolite, which are met with on the 
tips. 
“d) A pure white limestone, which is very uniformly and con- 
spicuously oolitic. 
This contains few fossils, but, by breaking up some scores of 
blocks, Terebratula globata was found to be not uncommon in it, 
and Rhynchonella subtetrahedra occurs sparingly. In places this 
oolite becomes blue or yellow, and the change of colour often 
occurs quite suddenly in a single block. In a large block, which 
exhibited the change from white to. yellow, the yellow portion was 
seen to be made up entirely of a thick mass of Thammnastrea. 
(2) A sandy and fine-grained blue limestone, in which Yerebra- 
tula globata is quite common and, with it, Rhynchonella subtetra- 
hedra, as well as a much-branched species of COladophyllia(?). 
This rock is consequently on about the same horizon as the last. 
Judging by the matrix alone, a specimen of Collyrites ovalis, which 
we obtained, came from this bed. 
(3) A deep yellow-stained limestone, containing abundant fossils 
embedded in a very compact matrix. 
In this rock the external impressions of costate Trigonice are 
extremely abundant, and perfectly typical specimens of Rhyncho- 
nella spinosa have been obtained from it. It is undoubtedly 
on the same horizon as a compact blue limestone which contains 
the same fossils, and of which labelled specimens from the boring 
of Shaft No. 4 are preserved. 
(4) A very compact, splintery, yellow limestone, containing 
numerous specimens of a well-marked species of Montlivaltia, inter- 
mediate between MV. lens and M. Delabecher. Since the greater part 
jn. GS. No, 232. 35 
