Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/141

1869.] those adopted by the President. This would be evident, so far as concerned Pterodactyles, from a work on Ornithosauria which he had just completed, and which would be published in a few days.

Mr. stated that the dolomitic conglomerate in which the Thecodont remains occurred near Bristol was distinctly at the base of the Keuper of the Bristol area, being beneath the sandstones and marls which underlie the Rhaetic series. There were no Permian beds in the area. He regarded the conglomerates as probably equivalent to the Muschelkalk. It was only at one point, near Clifton, that the Thecodont remains had been found.

Prof. was pleased to find that there was such a diversity of opinion between Mr. Seeley and himself, as it was by discussion of opposite views that the truth was to be attained. He accepted Mr. Etheridge's statement as to the age of the Bristol beds.



physical conditions which determine and accompany the existence of coral reefs, and the natural history of those vast aggregations of species of Madreporaria, have been sedulously and successfully studied ever since Darwin and Dana published the facts and theories which aroused the scientific world to a sense of their importance to geological reasoning. The physical geography of the Indo-Pacific and West-Indian seas has been investigated with as much care as the zoology of those marine banks which, fashioned by coral polypes, form a nidus for the existence of vast numbers of Invertebrata, fish, and birds. Nothing has been more satisfactorily determined than the scheme of the production of reefs, and the system of species-grouping that obtains in them.

The dependence of the coral polypes upon certain definite external conditions is as well understood as is that of the myriads of mollusca upon the flourishing state of the reef-builders. The dredge has done much to show the characters of the corals in the shallows and moderately deep seas of reef areas; and the species and genera frequenting them have been distinguished from those peculiar to the