THE (-.D RED SANDSTONE. 129 
in the Gray Sandstones which form on both sides the Tay, 
where the Tilestone formation seems wanting, the apparent 
base of the system. It is exclusively a medal of the middle 
empire. (See Note G.) 
In the last-mentioned locality, in a beautifully wooded dell, 
known as the Den of Balruddery, the Cephalaspis is found 
associated with an entire group of other fossils, the recent 
discovery of Mr. Webster, the proprietor, who, with a zeal 
through which geological knowledge promises to be materially 
extended, and at an expense of much labor, has made a col- 
lection of all the organisms of the Den yet discovered. 
These the writer had the pleasure of examining in the com- 
pany of Mr. Murchison and Dr. Buckland : he was afterwards 
present when they were examined by Agassiz; and not a 
single organism of the group could be identified on either 
occasion, by any member of the party, with those of the 
lower or upper formations. Even the genera are dissimilar. 
The fossils of the Lias scarce differ more from those of the 
Coal Measures, than the fossils of the Middle Old Red Sand- 
stone from the fossils of the formations that rest over and 
under them. Each formation has its distinct group —a fact 
so important to the geologist, that he may feel an interest in 
its further verification through the decision of yet another high 
authority. The superior Old Red Sandstones of Scotland 
were first ascertained to be fossiliferous by Professor Fleming, 
of King’s College, Aberdeen,* confessedly one of the first 
* The Upper Old Red Sandstones of Moray were ascertained to 
be fossiliferous at nearly the same time by Mr. Martin, of the Ander- 
sor Institution, Elgin. There is a mouldering conglomerate precipice 
termed the Scat-Craig, about four miles to the south of the town, 
more abundant in remains than perhaps any of the other deposits of 
13* 
