18 69. ] DAVIDSON——PEBBLE-BED BRACHIOPODA. via 
and others have been zealously at work collecting additional infor- 
mation, and every specimen that might assist in determining the age 
of the rock from which these drifted pebbles were derived has been 
carefully preserved *. 
The Brachiopoda were transmitted to me at various times for 
examination. I have studied and compared them, so far as this was 
compatible with the preservation of the specimens. These fossils 
occur in the shape of internal casts and external impressions only ; 
but by the aid of gutta-percha it was often possible to reproduce 
the external as well as the internal surface of both valves, and thus 
describe and figure the entire shell in as complete a manner as if taken 
from the sea. There are, however, a number of species which have 
occurred but once, or very rarely, and in so incomplete a state of 
preservation that it has frequently been impossible to arrive at a 
decided or satisfactory specific identification ; and in such a difficult 
problem as the age of these pebbles at Budleigh Salterton, one can- 
not be too cautious in the identification of the fossils which they 
contain. 
After the careful examination of several hundred specimens, I 
have been able to recognize from thirty-seven to forty species of 
Brachiopoda, besides many fossils referable to other classes. Of 
some of the former, descriptions have already been published in my 
Monograph of Silurian Brachiopoda. 
The rock or pebbles containing these fossils, as described by Mr. 
Vicary, ‘‘is generally a Sandstone, but sometimes so compact as to 
assume a quartzite character.” The colour of the rock is very varia- 
ble, being either white, grey, yellow, or more or less strongly tinted 
with red. The size of the boulders varies considerably ; they have 
been completely rounded and polished by the action of the waves 
over a rough bottom; and a comparatively small number scem to 
contain fossils. The pebble-bed, on the coast, in its thickest part, is 
not much more than 100 feet thick; it caps a ridge of hills running 
inland to the north full twelve miles, extending down both sides of 
these hills, in some places, to the extent of three or four miles. 
Most of the fossils are found near the coast; and I am informed that 
some few have been likewise met with in the Straightway pits, 
where pebbles are broken for the roads; but none were ever found 
in that locality by Mr. Vicary. The pebbles are largely distributed 
with flints in the gravel-beds of the neighbourhood7y. 
From the appearance of the pebbles and their accumulation in the 
cliff at Budleigh-Salterton and in other spots, irrespectively of their fos- 
sil contents, it would be natural to arrive at the conclusion that they 
all belong to a rock of the same age, transported thither at a period 
subsequent to its formation; and this view is, rightly or wrongly, 
entertained by several geologists. It has been likewise asked :—How 
can fragments of rock, varying in age, be accumulated in the same 
pebble-bed? They could not have come from different localities; and if 
* The discovery of by far the largest number of species is due to Mr. Vicary. 
t See also a paper, by Mr. Pengelly, ‘On the Denudation of Rocks in Devon- 
shire.” ; 
