368 ON THE CORALS OF THE 
saurus must have gambolled, and the goggle-eyed ichthyosaurus 
have darted along the tracts now traversed by the porpoise and 
the whale. 
Phe Oolitic deposits in the neighborhood of Helmsdale con- 
sist mainly of beds of a laminated, dark-colored, arenaceous 
shale (charged with ammonites and belemnites, serpula and ter- 
ebratula), which alternate with beds of a rough conglomerate, 
formed chiefly, as has been already intimated, of Old Red 
Sandstone materials. The corals, especially those of the genus 
Isastrea, occur both in the shales and the conglomerates; but 
it is amid the rocky masses of which the latter are composed that 
they seem to have grown; and in the shale we not unfrequently 
find them overturned, as if they had been torn with violence 
from their proper habitats on some stony ridge or hard bottom, 
and buried head-downwards in the mud. Corals, apparently 
of two different species, occur at Brora, but in so defective a 
state of keeping, that little else can be said regarding them than 
that they are said to belong to the genus Thecosmilia. In both, 
the corallum is composite and dendroid; but in the one the 
branches strike off at more acute angles than in the other. Its 
calices, too, are more rounded at their edges, and its septa less 
simple, more flexuous, and more prominently denticulated. So 
imperfect is their state of preservation, that neither species 
exhibits the exterior coating or epitheca characteristic of the 
genus. The place in the system in which they occur is higher 
than that of the beds at Helmsdale, but not higher than the 
base of the Great Oolite. And such are all the corals of the 
Oolitic system in Scotland with which the explorations of years 
have brought me acquainted. 
The other subject to which I purpose directing for a brief 
space the attention of the Society has a connection, rather in- 
cidental than direct, with the fossil corals of our country. On 
first acquainting myself, about ten years ago, with the massive 
