THE OLD RE) SANDSTONE. 123 
greatest of the three ; and there seems to be zodlogical as 
well as lithological evidence that its formation must have 
occupied no brief period. The same genera occur in its upper 
as in its lower beds, but the species appear to be different. 
I shall briefly state the evidence of this very curious fact. 
The seat of Sir William Gordon Cumming, of Altyre, is in 
the neighborhood of one of the Morayshire deposits discov- 
ered by Mr. Malcolmson; and for the greater part of the last 
two years Lady Gordon Cumming has been engaged in mak- 
ing a collection of its peculiar fossils, which already fills an 
entire apartment. The object of her Ladyship was the illus- 
tration of the Geology of the district, and all she sought in it 
on her own behalf was congenial employment for a singularly 
elegant and comprehensive mind. But her labors have ren- 
dered her a benefactor toscience. Her collection was visited, 
shortly after the late meeting of the British Association in 
Glasgow, by Agassiz and Dr. Buckland ; and great was the 
surprise and delight of the philosophers to find that the whole 
was new to Geology. All the species, amounting to eleven, 
and at least one of the genera, that of the Glyptolepis, were 
different from any Agassiz had ever seen or described before. 
The deposit so successfully explored by her Ladyship occurs 
high in the lower formation. Agassiz, shortly after, in com- 
paring the collection of Dr. Traill (a collection formed at 
Orkney) with that of the writer, (a collection made at Crom- 
arty,) was struck by the specific identity of the specimens. 
In the instances in which the genera agreed, he found that the 
species agreed also, though the ichthyolites of both differed 
specifically from the ichthyolites of Caithness, which occur 
chiefly in the upper beds of the formation, and from those 
also of Lady Cumming of Altyre, which occur, as I have 
said, at the top. And in examining into the cause, it was 
