Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/295

 this breccia deep under the plain of New Red (below the present sea-level) and overlying the coal-measures of the Somersetshire coal-pits. At Clevedon and Portishead it now fringes the sea-margin resting on Old Red, Carboniferous, and Pennant, whilst at Clifton, the Mendip Hills, the north part of the coal-basin, and numerous other spots, it occupies intermediate geographical sites, thus clearly showing a depression and reelevation of at least 1000 feet. During the whole of this amount of oscillation and accumulation of the Keuper marls and sandstones in the deeper portions of the sea, the conglomerates were forming along the margins, shallows, and shores of the palaeozoic land. These Dinosauria, then, from their place in time, or the elevated geographical locality they now occupy (which in this case is a measure of time), would appear to have lived during the later portion of the deposition of the Keuper ; be it remembered, however, that we have no proof of the Bunter beds ever having been deposited over the Bristol area. There is nothing whatever to show that these Dinosauria did not occupy this area, and live through the whole of the Triassic epoch. The chief difficulty is the realization of the affinities of these reptiles to any preexisting forms through the doctrine of evolution — as well as the area or province occupied by them, or from which they may have migrated. The question becomes one of the distribution of dry land during Praetriassic time, and also whether that land was occupied by Dinosaurian and Lacertilian types differentiated through descent during the lapse of time that occurred or was represented between the Palaeozoic and Mesozoic epochs. The limited area occupied by this peculiar conglomerate over the Bristol district, and the paucity of remains occurring in it, added to the fact that those found were evidently not deposited during its early deposition or history, render it doubly difficult to come to a conclusion or even hypothesis as to the probable distribution of these Dinosauria in time.

7. Zoological Contents or Patina of the Dolomitic Conglomerate.

With the exception of a few fossils derived from the Carboniferous Limestone and Millstone Grit *, upon which the conglomerate rests, only a few reptilian bones belonging to two genera have been discovered and assigned to the age of the conglomerate. These remains were first noticed and described by Dr. Riley and Mr. Samuel Stutchbury, of the Bristol Philosophical Institution, in the year 1836†, and were then the oldest known Dinosauria in Britain. These authors referred them to two reptilian genera Thecodontosaurus and Palaeosaurus, noticing their Megalosauroid affinities through the characters of the vertebrae and femora. Subsequent examination of these remains by Prof. Huxley has clearly established their true

- striata. Terebratula hastata. Chouetes hardrensis. Productus. Psammodus porosus. Cochliodus contortus. Lithostrotion junccum, - irregulare.
 * Spirifera cuspidata.

† Geol. Trans, vol. v. 2nd ser. p. 349.