116 LIAS OF ENGLAND AND WALES: 
excepting where it is diversified by faults that modify the strike 
of the ledges, or by heaps of boulder- shingle that lie here and 
there on the surfaces of the platforms. 
The following general sequence is shown : the upper beds being 
more jointed and open, springs are thrown out at their junction 
with the bluer beds : 
("Yellowish argillaceous limestones ; about 55 bands, on the 
7o 'i whole thicker than the beds below and with less clay the 
A .. J limestones here and there exhibiting rhomboidal jointing.* 
T) ,j i- "S Bluish-grey limestones ; about 80 comparatively thin and on 
n ' J the whole irregular bands, alternating with thin clays, shales, 
(_ or marls. 
Southerndown Series, &c. 
The lower division attains a thickness of about 80 feet esti- 
mated from the top of the conglomeratic series ; and in the first 
cliff beyond the angle formed by the Dunraven headland, the 
lower beds are shown to a height of about 70 feet, and the upper 
occupy about 50 feet above. The cliffs between the gullies of 
Cwm-mawr and Cwrn-bach, rise to a height of 200 feet, so that 
the limestone-series here exceeds that thickness, though not 
perhaps to any great extent. We do not however notice any 
beds in the cliffs as far as Aberthaw, that indicate any other 
divisions of the Lower Lias, and judging by the fossils, the beds 
belong to the zones of Ammonites angulatus, A. Bucklandi, and 
A. semicostatus, and mainly to that of A. Bucklandi. 
On the whole the beds are tolerably flat, but with a general 
inclination (interrupted by a gentle anticlinal) towards Nash 
Point. Approaching this point, a thick mass of limestones appears 
on the top of the yellow beds in the cliffs, forming a conspicuous 
band as at Southerndown, and this caps the buttress of Nash 
Point. Here, then, the cliff is formed of a thick mass of lime- 
stones, resting on tolerably thick beds of limestone, bluish and 
yellowish, and these again on bluish limestones, on the whole 
even-bedded with here and there crinkly layers and thin partings 
of shale. The limestones form thick ledges and pavements of 
rock, varying in direction with the inclination of the beds, and 
the changes produced here and there by fault;?. Gryphaia 
arcuata, Lima ffigantea, and Ostrea, occur, often in clusters, 
together with Pentacrinus, small Ammonites and occasionally 
lignite. (See p. 43.) Pholadomya appears not uncommon in the 
higher jointed beds, fallen masses of which lie on the beach. 
The cliffs below the Nash lighthouses, show the thick mass of 
limestones towards the upper portion of the cliff?, and this is let 
down to lower levels here and there by faults which thus counteract 
the influence of the dip. In one instance, not far from Dunraven, 
a small fault, which displaced the upper beds 2 or 3 feet, was lost 
towards the base of the cliff, the layers of limestone being just 
* These beds are very similar in character to the Black Limestone locally known 
ns " Aberdo Limestone," iu the upper part of the Carboniferous Limestone of 
Flintshire. A. Strahan, Geol. Rhyl (Mem. Geol. Surv., Sheet 79, N.W.), pp. 15, 16. 
