326 ON THE ANCIENT GRAUWACKE 
resembling those of the common Sertularia halecina, we find, 
on examination, that they are in reality restricted to one side, 
and that the apparent fringes of the other are but mere notches 
in the stem. In one respect, however, judging from the rocks 
in which we usually find them, these organisms must have re- 
sembled the sea-pens. ‘There is a deep submarine ravine, which 
runs for some distance along one of the middle reaches of the 
Moray Frith, and at the steep edges of which the water deepens 
suddenly from about twelve to about thirty fathoms. The 
bottom on either side is gravelly and hard, whereas the ravine 
is charged with a dark adhesive mud, abounding in fish bones, 
and which intimates to the sense of smell, when brought to the 
surface, that there must have entered into its composition no 
small portion of organized matter. Now, this muddy ravine 
abounds with sea-pens. When not a specimen can be procured 
on the hard ground on either side, the fisherman’s lines, when 
his boat drifts across the hollow, becomes charged with them: 
every muscle bait brings up attached to it what the fishers of 
the Frith term its “sea-tree ;” so that specimens may be pro- 
cured by the hundred. And from the dark-colored, finely- 
grained, semi-bituminous character of the slates in which the 
graptolites chiefly occur, it is apparent that they also loved a 
muddy habitat. 
T have now to refer to but two other papers on our Scotch 
Grauwacke. In 1849, Professor Nicol made the Silurian 
deposits of the south-east of Scotland the subject of yet another 
very able memoir, in which he specified several new localities 
for its fossils, and added to the previous list at least one new 
fossil more,—a hitherto undescribed species of Graptolite. 
He bestowed much care, too, in ascertaining the general direc- 
tion of the beds and mountain ranges of our southern High- 
lands; and found it coincident, on an average drawn from no 
fewer than sixty-six several observations, with the direction of 
