﻿Vol. 6 1.] THE KH^TIC DEPOSITS OP GLAMORGANSHIRE. 391 



above the average level (see fig. 1). Frequently a black-shale 

 deposit is found filling-in these irregularities ; but it is occasionally 

 replaced by a soft yellowish - green marl, which passes up 

 gradually into a blackish marl. At that part of the cliff where 

 these notes were made, a layer of grey argillaceous nodules, with 

 quartz-pebbles and fish-remains, rested upon the above-mentioned 

 marl or shale. Doubtless this band of nodules is intimately connected 

 with the ' fish-bed ' for which the locality is celebrated. The fact 

 that black shale is intercalated between the ' fish-bed ' and Sully 

 Beds in places, is commented upon by Mr. F. T. Howard, F.G.S., 

 who, like most observers, had regarded the ' fish-bed ' as the lowest 

 Khgetic deposit in the Cardiff district. 



'I was therefore,' he wrote, 'surprised, on removing a block of the con- 

 glomerate ['fish-bed'] from its natural position on the foreshore opposite 

 Lavernock Point, to see beneath it and lying directly on a worn surface of 

 Tea-Green Marls, a thin band of black shale, not more than ^ inch thick, 

 containing numerous crushed specimens of typical Ehaetic shells — Gardium 

 rhcBticum, Avicula contorta, and Pecien valoniensis. Others may have been 

 represented, but were badly preserved. The band of shale was very 

 irregular. . . . 1 



There arc places where the ' fish- bed ' rests directly upon the 

 marlstone of the Sully Beds. As noticed by John Storrie, the ' fish- 

 bed ' is not continuous, but occurs in patches, and the best of these 

 will be found protected by seaweed between low- and high-tide 

 marks : — 



'The patches in which it occurs vary from the size of a sixpence to pieces 

 5 or 6 yards square, and at some places are comparatively close together — at 

 others a considerable distance apart. The bed may be best described as a 

 conglomerate of pure white quartz-pebbles, from the size of a hen's egg down- 

 ward, all waterworn, and mostly crusted with a greenish-copper tinge, jasper- 

 like pebbles, and also some waterworn pieces of limestone (unfossiliferous, but 

 probably Silurian, from their general texture).' 2 



I am inclined to agree with Mr. Howard that the last-mentioned 

 pebbles are more likely to be "of marlstone derived from the Sully 

 Beds. A fine piece of this ' fish-bed,' not altogether of the usual 

 lithic structure, since the greater mass of it consisted of quartz-sand 

 cemented together mainly by carbonate of lime, contained in great 

 abundance the teeth of Acrodus minimus, Gyrolepis Alberti (?), 

 Saurichihys acuminatus, Sargodon tomicus, and Lepidotus ('!)* and 

 less commonly of Hybodus minor and H, cloacinus. Rich as this 

 deposit is in vertebrate-remains, it has not been regarded by our 

 chief authorities as the Bone-Bed. It may be suggested that this 

 basal bone-bed at Lavernock is the equivalent of a deposit of a 



1 Trans. Cardiff Nat. Soc. vol. xxix (1896-97) p. 66. 



2 Ibid. vol. xiv (1882-83) p. 100. 



3 The teeth thus denominated are those described by Agassiz as Spfaerodus 

 minimus, and by Meyer & Plieninger as Psammodus orbicularis. They may 

 belong to the same animal (Sargodon tomicus) as the chisel-shaped teeth, but at 

 present it appears desirable to keep the records separate. Charles Moore thought 

 that the knob-like teeth probably belonged to Lepidotus, and such teeth are 

 recorded in this paper as ' Sarqodon tomicus' (Lepidotus?). See Quart. Journ. 

 Geol. Soc. vol. xvii (1861) p. 499, footnote. 



