1870. ] ETHERIDGE—BRISTOL DOLOMITIC CONGLOMERATE. 175. 
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 Palcosaurus. 
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 paleozoic rocks of the Bristol coal-basin. 
2. History. 
So long ago as the days of Richard 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 Reptilia occurring in many parts 
of Kurope, 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 paleon- 
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. Riley 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 Dinosauriar‘. 
This singular deposit is locally called the Magnesian or Dolomitic 
Conglomerate ¢, so termed from the presence of dolomite, or carbo- 
* Quart. Journ. Geol. Soe. yol. xxvi. p. 12: ‘On the affinity between the Di- 
nosaurian Reptiles and Birds.” “On the classification of the Dinosauria, with 
observations on the Dinosauria of the Trias,” ibid. p. 32. 
+ 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 
