1867.] BEISTOW LOWER LIAS OF GLAMOEGANSHIRE. 203 



to be those exposed at the line of old quarries between Sutton and 

 Craig-yr-eos, may come in thus. 



"Whether this be the case, or not, will not affect my argument, 

 the object of which is merely to prove that the beds between the 

 Carboniferous Limestone and the common argillaceous Lias limestone 

 and shale, which cover a large area between Sutton and Cowbridge 

 (at Ewenny, Brocastle, Llangan, Pentre Meirig, and other places), form 

 a part of the Liassic series, the difference in the lithological 

 character being due to the prevalence of special conditions at the 

 period of their deposition. 



Having satisfied myself, thus far, that the Sutton and Southern- 

 down series of Mr. Tawney are stratigraphically part of one 

 series, I directed my attention more particularly to the fossils ; and 

 the result enables me to assert that the group of strata in question 

 is true Lias from top to bottom. 



The four commonest and most characteristic Lias fossils may be 

 traced from the very lowest of the beds into their junction with the 

 ordinary Lias ; and when I state that Qryphcea incurva, Ostrea 

 Liassica, with Lima gigantea and Ammonites of large size, have been 

 recognized in the rocks of this series, in place, I think that the 

 Liassic age of these deposits may be regarded as fairly proved. 



It is true that these fossils are somewhat sparingly distributed in 

 the coast-section, and that the rocks are so hard that, even with the 

 help of so experienced a collector as Mr. Gibbs, the number of speci- 

 mens procured is scanty. Still they are sufficient to prove the case. 

 In a conglomeratic deposit of this nature it is to be expected that 

 fossils should be but sparingly present ; and the Corals found in the 

 Sutton Stone, especially between Sutton and West, partly consist of 

 Palaeozoic * species derived from the Carboniferous Limestone, which 

 is there crowded with them, and out of which they have been 

 washed during the denudation of the Carboniferous Limestone, 

 which accompanied the deposition of the Sutton Stone. 



Although aware that exceptions will be made to the statement of 

 the occurrence of GrypTicea incurva and Ostrea Liassica in these 

 beds, and that the fossils in question will be pronounced by some 

 authorities, whom I hold in great respect, to be Gryplima irregularis 

 and Ostrea irregularis, it is nevertheless my belief that the Oryphcea 

 of the beds in dispute, if not identical in form with Grypliea incurva^ 

 is yet the representative and only a variety of that shell, which oc- 

 curs in such remarkable numbers in the Lias immediately above, the 

 slight variation in their respective forms being a result of difference 

 of conditions ; and similarly as regards the Ostrea. 



Probably, by means of a large collection of the shells in question, 

 it might be possible to trace all the gradations between one form 

 and the other. In fe,ct it is stated by Dr. Duncan that '^ doubtful 

 specimens of Gryphcea incurva are now and then met with in the 

 Brocastle beds. * * * * One specimen from Brocastle has the 



* Dr. P. M. Duncan, Quart. Journ. G-eol. Soc. vol. xxii. p. 89, 1865; also 

 vol. xxiii. p. 13, 1866. 



VOL. XXiri. PART I. Q 



