70 PItOCEEDIN0S OF THE GEOLOGICAL SOCIETf* [DeC. 6, 



peculiarities of the Avicula-contorta series at their most westerly 

 boundary in Great Britain ; to discuss the " Sutton Stone " as to its 

 stratigraphical, lithological, and palseontological relations; to show 

 from organic remains that its affinities are with the Triassic forma- 

 tion, and not with the Lias as commonly supposed, and then to claim 

 it as Rhaetic, and in so doing to extend, for the first time in England, 

 the range of Ammonites down into the Ehsetic series. 



At the Bath Meeting of the British Association for 1864, Sir R. 

 I. Murchison announced the presence of the argillaceous limestones 

 and shales of the Rhsetic series in a small outlier of Lias (as mapped) 

 close to Pyle Station (west of Bridgend) ; and having in this way had 

 my attention directed to the subject, I found that the Avicula-contorta 

 strata were widely extended in this district ; and as they show some 

 peculiarities here, I will begin by a few remarks on these beds. 



2. Pyle district. — The above-mentioned patch, sufficiently described 

 by Mr. Bristow*, consists of buff-coloured marls and greyish-brown 

 shales and limestones, which last, from their appearance and con- 

 choidal fracture, remind one of the Gotham marble : these are pro- 

 bably high in the series ; they are mapped as lying on the Keuper. 



A few hundred yards south of this we reach the southern limit of 

 the Keuper in this district. It consists of red marls with buff and 

 green marls resting upon them ; the same conditions occur at the 

 base of the Ehaetic series at Wenvoe, Barry Island : and besides this, 

 there is very little of the New Red series in this district ; what has 

 been hitherto called Keuper is much of it Rhsetic. 



I am obliged to dissent from the opinion expressed by Sir H. De la 

 Beche in his comprehensive and admirable memoir on the " Forma- 

 tion of Rocks in South Wales"t, that the sandstones near Pjde church 

 are inferior to the red marl lately spoken of : the district is more 

 broken by faults than is expressed in the map of the Geological 

 Survey ; and this may have caused some ambiguity. 



The sandstones at the base (10-12 feet thick) are in places much 

 weathered, the iron being changed to peroxide, and the mass crum- 

 bling to rusty sand under the hammer ; others are unoxidized and 

 harder, namely the pale-green or yellow thick sandstones, affording 

 when dry a good building- stone : some of these beds are very similar 

 to the white Keuper sandstones near Bridgend. Above these are hard, 

 green- and- white mottled and purple marls. These belong to the 

 Avicula-contorta series, and not to the Keuper. The search for fossils 

 is frequently unsuccessful here, from the oxidation of the beds, due 

 to exposure to moisture and air. On the quarry-refuse heaps are 

 found great numbers of a small species of Natica crowded together 

 by hundreds ; Anatina prcecursor also is abundant. The fossils of 

 these sandstones, which are exceedingly fossiliferous on Stormy 

 Down and near Laleston are 



Myophoria postera, 

 Natica Pylensis, 

 Anatina precursor, 

 Modiola minima, 



Saurichthys apicaHs, 

 Acrodus minimus, 

 Avicula contorta, 



Axinus elongati 



depressus, 



cloacinus. 



* Eeport Brit. Assoc, Bath, 1864, Trans. Sections, p. 60. 

 t Memoirs of the Geological Siu'vey, vol. i. p. 252. 



