ZONE OF AVICULA CONTORTA. 167 



and Nemacantlius filifer, Ag. The Bone-bed rests upon four feet of black unfossiliferous 

 shales, very fissile and papery ; and this bed, parted by a ferruginous band in the 

 middle, rests upon a very irregular bed of grey, earthy, fine-grained sandstone, graduating 

 downvi^ards into a grey earthy limestone, containing lignite and some fishes' scales, marked 

 {v) in the section ; this is the last trace of life observed in the Marls which lie beneath, 

 consisting of eighteen feet of cream-coloured, grey-green, and pale-red marly limestones, 

 breaking up into unfossiliferous cuboidal masses ; which overlie two feet of greenish- 

 grey marls, breaking up like the preceding beds, and having thin seams of gypsum 

 filling some oblique and vertical joints. These rest upon the deep-red marls of the 

 Keuper beds. 



This detailed section of the Penarth cliffs^ may be considered as the complement to 

 my notes on the same at p. 10, and the vertical profile now introduced will enable the 

 reader to make an interesting and instructive comparison between the Avicida contorta 

 zone at Garden Cliff (fig. 1, p. 7), Aust Cliff (fig. 2, p. 8), and the fine coast section at 

 St. Audrey's Slip, near Watchett (p. 12). It will be observed that a certain amount of 

 uniformity prevails throughout the series exposed on both banks of the Severn and on 

 the opposite shores of the British Channel, whilst in the Palaeontology of the different 

 beds certain differences are noted which deserve study. Thus, the Estheria-hed and 

 underlying shales, so characteristic of Garden Cliff, are not found at Penarth, but appear 

 to be represented by a set of strata which occupy the position of the Lower White Lias 

 series of Dorset and Somerset. 



The Pallastra-sandstone, with its large slabs of ripple-marked ledges, the ripples being 

 parallel to the strike of the bed, and which sandstone is interposed between upper and 

 lower bone beds at Garden Cliff, is absent at Penarth and the other localities. 



The Bone-bed at Aust, with its large Ceratodus teeth, representing several species of 

 fossil fishes, and numbering many hundreds of individuals is unique. I am not aware 

 that the teeth of this genus of fishes are found in any other Rhsetic Bone-bed in the 

 British islands. The assemblage in the Bristol Museum was collected through several 

 years by Mr. Higgins, and purchased from him by subscription for the Institution. 

 Professor MialF has lately figured and described several of these fossils, to which I beg 

 to refer. 



1 See Mr. Etheridge's description and woodcut in the ' Transact. Cardiff Nat. Soc.,' vol. iii, part 2, 

 pp. 48, &c., 1872. 



^ Palseontographical Society's vol. for 1878, 'On Sirenoid and Crossopterygian Ganoids,' pp. 27 — 32, 

 PI. II— V, 1878. 



