TRANSACTIONS OF THE SECTIONS. / 7 



then proceeded to point out tliree remarlcable outliers of Mountain-liniostoiio occur- 

 ring at LiR-kingtou and Vobster immediately to the north of the Meudip Hills, 

 which, owing- to their abnormal position, had long been the subject of curious 

 speculation, and concerning which diftereut authors had arrived at very opposite 

 conclusions. The dimensions and situation of these limestone masses were de- 

 scribed in detail. The largest of the three occurred at Upper Vobster, and mea- 

 sured 1150 yards in length by 300 yards in breadth ; another at Luclnngton was 

 450 yards in length by l20 yards in breadth ; while a third, called the Tor Rock, 

 was of smaller dimensions. They were completely surroimded by Coal-measures, 

 and occurred at a distance of from 1300 to 1900 yards from the principal outcrop 

 of limestone in the Mendip range. 



The writer then proceeded to explain the views of other writers on the subject, 

 which may be classed under three heads :— First, the original fault theory of Dr. 

 Bucldand and the Geological Survey ; second, the combined fault and anticlinal 

 theory of Mr. H. B. Woodward; and third, the overthrow theory of Messrs. 

 Greenwell, Moore, and others. As to the first two theories, he said the workings 

 of adjacent collieries had failed to show any proof of their existence. He then 

 proceeded to prove that the limestones in question were superficial maases of no 

 great thickness, and that they did not extend downwards to connect with the 

 great underlying mass of Mountain-limestone, for the workings of several mines 

 and one or two wells had proved the existence of Coal-measures beneath them at a 

 comparativelv shallow depth. 



He expressed his belief in the theory that, during the upheaval of the Mendips 

 and the inversion and crumpling-up of coal-strata which accompanied it, the 

 limestone masses of Luckington and Vobster were in some way carried over from 

 the Mendip range, and so rested upon the Coal-measures instead of lying far be- 

 neath them. The paper was explained by numerous diagrams and sections, the 

 latter showing that the Mendips had originally attained a much higher elevation, 

 and that the limestone strata removed by denudation were probably more nearly 

 vertical than those which remain, if indeed the beds were not partially folded over 

 in the same way as the Coal-measures. 



On the Age of the Durdham Down Deposit, yieUlng Thecodontosaurus ^-c. 

 By Chaeles Moore, F.G.S. 



About forty years ago some conglomerates were opened up apparently resting on 

 the Carboniferous Limestone of Uurdham Down, in which were found scattered 

 reptilian remains, described by j\Iessrs. Eiley and Stutchbury under the names 

 Thecodontosaurus and Falceosaurics. They were then supposed to be of Permian 

 ao-e, but are now refen-ed to the Magnesian Limestone. The author believed them 

 to be still more recent, and that they belonged to the Ehretic period. 



In support of this conclusion he referred to a paper by himself published in the 

 ' Geological Journal ' for 1807 *, in which he showed that over a large area in the 

 Mendip district the Carboniferous Limestones had formed the floor of the seas of 

 more recent geological epochs, and, having become fissured, those fissures had 

 been filled with the organic and other contents of more recent periods, these being 

 shown to be as wide apart as from Rhcetic to Liassic times. In veins of the former 

 ao-e he had found a fauna of great interest, including the reptilia Thecodontosaurus 

 and Palaosaurus, foimd only before at Durdham Down, and amongst the fish- 

 remains numerous examples of Saurichthys ajficalis and Acrodus 7nitn))tns. ^ 



The author then showed that precisely similar physical, mineralogical, and 

 palteontological conditions were to be found on the tableland of Durdham Down, 

 where numerous veins, one of them 18 feet in thickness, traversed the Carboniferous 

 Limestone. One of these, near the Zoological Gardens, was proved to be of the 

 an-o of tlie Lower Lias — Ammonites, Echini, Foraminifera, and other remains of 

 that age being exhibited by the author taken from between the walls of the Car- 

 boniferous Limestone 30 feet from the surface. In another vein near the Suspension 



* " On Abnormal Conditions of Secondary Deposits &c. when connected with the So- 

 mersetshire and South Wales Coal-basin." 



