﻿Vol. 6 1.] CONTIGUOUS DEPOSITS OF GLAMORGANSHIRE. 403 



Mr. Cantrill has noticed some P^c^n-Limestones between Ty-ganol 

 and Pentre. 



At Pentre certain White-Lias beds have been preserved as an 

 outlier; also a few Rhsetic beds, as proved by pieces of Pecten- 

 Limestone with fragments of Pecten (Chlamys) valoniensis. This 

 outlier is situated 200 yards east of the road, and owes its preserva- 

 tion to faulting, whereby the beds composing it have been let down 

 on the north against the Carboniferous Limestone. Formerly 

 there was a quarry here, but now the excavation is filled with 

 water. On the south side of this pond the following beds are 

 exposed : — 



Thickness in feet inches. 



Clay, yellow, shaly at the base : visible 1 



Limestone, brown and dark-coloured ; Plicatula intus-striata 



common ] 5 



^ Clay 3 



Limestone 2 



Clay, yellow 5 



Limestone ; Modiola minima common 2 



^Shales, dark, hard, with thin beds of limestone seen 1 6 



The uppermost limestone in the foregoing record exactly resem- 

 bles the bed bearing a similarity to the Sun-Bed at Barry (p. 398). 



The account of these Rhsetic beds given by Mr. Cantrill shows 

 that, in the St. Hilary district, few if any exposures escaped his 

 attention. But there are one or two interesting facts not as yet 

 recorded. By the side of a pond, indicated by the arrow on the 

 Geological-Survey Map, and some 300 yards to the west of Garn, 

 is a limestone-bed very much resembling, lithically, a certain 

 development of the Estheria-Bed of North-West Gloucestershire. 

 This stratum contains Pseudomonotis fallax, and dips gently to the 

 north-east by Dorth : it is, therefore, most probably on the same 

 horizon as the Pseudomonotis-Bed. 



In the floor of the lane between St. Hilary and St. Hilary 

 Common, there is a quite fossiliferous bone-bed. The deposit is a 

 pale, slightly-arenaceous limestone, containing obscure casts of a 

 lamellibranch (Sdiizodus ?), scales and teeth of Gyrolepis Alberti, 

 Acrodus minimus, and a few indeterminable fragments of bone. 2 



In the roadside at The Cross, south of St. Hilary, the Bhaetic 

 sandstones are exposed. There is, however, a considerable amount 

 of black shaly matter present, and in the sandstone-layers inter- 

 calated in this shale — especially in that about an inch thick towards 

 the middle (vertical) of the exposure — 'plant-remains' are abundant. 



1 A rock crowded with this lamellibranch, but not found in situ, is assigned 

 to this horizon, owing to the similarity of lithic structure. 



2 See also Buckland & Conybeare, Trans. Geol. Soc. ser. 2, vol. i (1824) 

 p. 301 ; and ' The Geology of the South-Wales Coalfield : Pt. vi— The Geology 

 of the Country around Bridgend ' Mem. Geol. Surv. 1904, p. 41. 



2 G 2 



