﻿402 ME. L. RICHARDSON ON THE RHiETIC AND [Aug. I905, 



grouped with the Sully Beds. The fossils recorded from the lime- 

 stone-bed were observed mostly in the uppermost portion. Above 

 is a deposit of soft marl, which yielded single examples of Pterin 

 (Avicula) contorta, Modiola (indeterminable), and Hybodus minor 

 (tooth). 



The most interesting stratum in the foregoing section is the 

 Conglomerate-Bed distinguished as 15. 



In a series of deposits such as the Rheetic, it is often difficult 

 to correlate with certainty the various component deposits seen 

 at different localities. In certain districts, however, as in 

 North-West Gloucestershire and Worcestershire, the same lithic 

 characters are preserved by a bed over a considerable area ; but in 

 Glamorganshire such is not the rule, and as the beds are traced 

 westwards there is increasing evidence of the proximity of land. 

 Here, at TregyfT, the Lower Rhsetie was deposited close to a shore- 

 line composed of Carboniferous rocks, and as a result the Secondary 

 rocks became what Charles Moore would have termed ' abnormal.' 

 Therefore, it will be understood that when in the foregoing record, 

 and in those of sections farther west, a bed is distinguished by a 

 certain number, that number suggests rather than implies 

 contemporaneity with a similarly-notated deposit elsewhere. 



Mr. E. B. Wethered, F.G.S., has kindly supplied me with the 

 following notes on certain limestone- and chert-pebbles from the 

 Conglomerate-Bed : — 



' Limestone-pebble from the Conglomerate-Bed, Tregyff, near Cowbridge. — 

 An impure limestone containing a number of organic remains, but so altered 

 by molecular change that it is very difficult to determine them beyond a few 

 spines, crinoid-ossicles, fragments of polyzoa and mollusca. The main feature 

 of the slide is the presence of a large number of crystals of salt and gypsum, 

 which are apparently of secondary origin.' 



' Chert-pebble from the Conglomerate-Bed, Tregyff, near Cowbridge. — 

 Looked at in a hand-specimen this appears to be a chert enclosing oolite- 

 granules. The sections of this chert seen under a microscope show it to 

 contain a number of ovoid bodies, some of which include a nucleus, but the 

 usual form of concentric structure characteristic of oolite-granules is not 

 apparent. Originally the rock was probably a limestone, which has been 

 transformed into chert by the gradual replacement of the carbonate of lime 

 by silica.' 



The Pecten-Be&s (7 & 5 b) are well-developed ; but the super- 

 incumbent deposits are difficult to correlate, both on account of the 

 lack of distinctive fossils and the growth of vegetation, which 

 obscures the upper portion of the section to a large extent. 



In the neighbourhood of Ty-ganol the lower portion of the Lower 

 Rhsetic consists mainly of a sandstone-deposit. This sandstone is 

 well exposed by the roadside, 180 yards north-east by north of 

 Ty-draw, and therefrom were obtained a specimen of Hybodus minor 

 and a few scales of Gyrolepis Alberti. The whole of the lower 

 stage, however, is not replaced by an arenaceous deposit, because 



