312 ME. 0. A. SHRTJBSOLE ON TRIASSIC PEBBLES OE [Aug. I903. 



In 1876 1 Mr. Ussher contributed a paper to the Journal of this 

 Society, ' On the Triassic Rocks of Somerset & Devon.' Referring 

 to the Pebble-Bed, he indicated three distinct types of the formation 

 which appeared to pass one into the other horizontally, the Budleigh- 

 Salterton pebbles being succeeded northward by beds with small 

 pebbles of quartz and grit, and finally by a conglomerate containing 

 limestone-grit. This was followed in 1879 by a paper by the same 

 author on ' The Triassic Rocks of Normandy & their Environments.' 2 

 He considered that the Keuper alone was represented in that area. 

 Referring to the quartzites of May, he noticed a perfect litholo- 

 gical resemblance between them and some of the Budleigh-Salterton 

 pebbles ; but, on the hypothesis that the latter were a marine 

 deposit, he saw no way of accounting for their transport from Nor- 

 mandy in Bunter times. 



In 1880 appeared a paper in the Geological Magazine 3 by Prof. 

 Bonney, ' On the Pebbles in the Bunter Beds of Staffordshire.' The 

 various classes of pebbles were referred to and described ; and, as a 

 result of the study of the deposit as a whole, it was considered that 

 the Conglomerate might represent the deltas of two large streams 

 descending respectively from the north-west and the north-east. 



The existence of quartzites in the vicinity of Loch Maree strongly 

 resembling the light-coloured quartzites of the Bunter, also the 

 marked resemblance between theTorridon Sandstone and the quartz- 

 felspar grits of the Bunter, were adduced in support of the view 

 that the pebbles of the Bunter came chiefly from the north. A 

 second kind of quartzite was noticed in the Bunter pebbles, and 

 this occasionally was found to contain fossils. 



In the same year Thomas Davidson 4 described the Brachiopoda 

 of the Gres Armoricain of Britanny (Lowest Llandeilo). It is 

 characterized by Lingula Lesueuri, L. Haivkei, L. Salteri, and Dino- 

 bolus Brimonti, 



' species that have not hitherto been discovered in any rock, in situ, in Great 

 Britain.' 



All these species occur in the Budleigh-Salterton pebbles. He was 

 inclined to look for the parent rocks 



1 to France, or to an extension of Silurian and Devonian rocks that may have 

 existed in the Channel and nearer to Devonshire.' 



The whole subject was reviewed by Mr. Jukes-Browne in the 

 eighth chapter of his book on ' The Building of the British Isles ' 

 2nd ed. (1892). He supported Prof. Bonney's view that the pebbles 

 were brought into the Bunter by fluviatile agency ; and said that, 

 if some of the Budleigh-Salterton pebbles were really identical with 

 those of the Midland Bunter, 



' their existence in the south would suggest a common source in the tract which 

 separated the two areas of deposition.' [Op. cit. p. 193.] 



He quoted the investigations of Dr. Sorby and J. A. Phillips on 



1 Quart. Journ. Geol. Soc. vol. xxxii, p. 367. 2 Ibid. vol. xxxv, p. 245. 

 3 Dec. 2, vol. vii, p. 404. 4 Geol. Mag. 1880, p. 337. 



