176 PROCEEDINGS OF THE GHOLOGICAL SOCIETY, (Jan. 12, 
nate of lime associated with carbonate of magnesia, forming a pasty 
cement by which the rounded boulders and pebbles constituting the 
deposit are firmly held together; it is not to be confounded with 
the Permian magnesian limestones of the N.E. of England. The 
proportion of lime and magnesia appears to be indefinite in the 
uncrystallized dolomite, which is a mere mixture of true dolomite 
and carbonate of lime. 
Messrs. Buckland and Conybeare were the first to apply the 
term ‘‘ dolomite” both to this formation and to the carboniferous 
limestone when dolometized in situ, or so-called dolomitized lime- 
stone. 
In 1817 Mr. Warburton * had previously stated with reference 
to the conglomerate and associated New [ted Sandstone in the 
neighbourhood of Bristol and the Mendip Hills, that “if denudatory 
or other disturbing causes were in action previously to the depo- 
sition of the red marl, we might expect to find the red marl im- 
mediately incumbent upon any rock from the coal-measures to the 
granite inclusive.” 
Buckland and Conybeare in 18227 showed that the older and 
disturbed rocks of the Bristol district were not only covered uncon- 
formably by various beds of the New Red Sandstone series, but also 
that higher formations, such as the Lias and Oolite, were brought into 
contact with them in the same relative position. 
Messrs. Riley and Stuchbury subsequently had occasion to notice 
these beds under peculiar and interesting circumstances, announcing 
at the same time the discovery of two genera of reptilia in this 
conglomerate on Durdham Down, near Bristol; these they respec- 
tively named Thecodontosaurus and Palewosaurus. From that time 
to the present no occasion has arisen to call attention to these appa- 
rently uninteresting rock-masses, which, however, locally are of much 
importance. 
I should, however, here mention that my valued friend, W. San- 
ders, Esq., F.R.S., of Clifton, durmg the construction of his large 
geological map of the Bristol coal-field was so impressed with the 
belief that the Dolomitic Conglomerate occupied in some places the 
lowest part, and in others the middle (in time) of the Keuper 
series, that he purposely omitted inserting the conglomerate as a 
separate formation upon his map, but incorporated or massed it 
with the New Red Sandstones and marls, calling the whole the 
Keuper marls and sandstones. His map therefore fails to show the 
geographical position of the conglomerate on the higher or more 
elevated tracts of land surrounding the Bristol coal-field. That he 
was right in associating it with and placing it at the base of the New 
Red Sandstones and marls cannot be doubted; and the numerous 
sections and conditions under which I have examined it, both in the 
with the so-called magnesian limestone of Gloucestershire and Somersetshire 
(which forms part of the dolomitic conglomerate), or with the conglomerate itself. 
* Trans. Geol. Soc. vol. iv. p. 209: 1817. 
t+ Trans. Geol. Soc. 2nd ser. vol. i. p. 217, &c. 
+ Constructed upon the scale of 4 inches to the mile. 
