lately been so ably treated by Prof. Huxley. This paper is there- fore devoted to a consideration of the geological position and geogra- phical distribution of the conglomerate so widely spread over the Bristol area, and containing the remains of the Dinosaurian reptiles Thecodontosaurus and Palceosaurus.
I have little to communicate that has not been noticed by the older writers ; and the mention of the names of Bright, Gilby, Buckland, Conybeare, De la Beche, and Murchison, will show how little is left for me to do ; but uninviting as this nearly unfossili- ferous rock may appear at first sight, it nevertheless possesses a history even yet not written, and its origin, date, and fauna are still matter for investigation and research.
This old breccia is a grand and striking feature over many parts of the area where it is well exposed, and is a marked condition in the geological history and physical structure of Britain, to be studied and understood only over the limited and complicated area occupied by the palasozoic rocks of the Bristol coal-basin.
2. History.
So long ago as the days of Bichard Bright and Dr. Gilby, in 1811-16, the age and position of the dolomitic conglomerate of the Bristol area perplexed geologists.
The late able papers by Prof. Huxley, communicated to this Society *, have again opened up the question in connexion with the position in time and space to be assigned to two genera of Dino- sauria, a question of much interest, as tending to clear up the age, position, and distribution of certain Pep til ia occurring in many parts of Europe, Asia, Africa, and America. Again, the relation of the conglomerate in question to the older rocks on which it rests, as well as to the sandstones and marls associated with it, is a matter of much local interest.
I propose discussing this question on physical grounds only, and as an accompanying paper to that of Prof. Huxley upon the palaoon- tological contents of certain rocks in the Bristol area called dolomitic conglomerate.
The only remains ever found belonging to the dolomitic conglo- merate were described by Messrs. Biley and Stuchbury in their able paper in the ' Transactions of the Geological Society,' vol. v. 2nd ser. p. 349, read in 1836 (published 1840) ; and lately much additional matter has been added by Prof. Huxley in his paper upon the classi- fication and affinities of the Dinosauriaf .
This singular deposit is locally called the Magnesian or Dolomitic Conglomerate £, so termed from the presence of dolomite, or carbo-
- Quart. Journ. Geol. Soc. vol. xxvi. p. 12 : " On the affinity between the Di-
nosaurian Keptiles and Birds." " On the classification of tbe Dinosauria, with observations on the Dinosauria of the Trias," ibid. p. 32.
t Quart. Journ. Geol. Soc. vol. xxvi. pp. 32-50.
} The Yorkshire and Nottinghamshire dolomite or magnesian Limestone is an independent member of the Permian, and must not be confounded either
