60 
NOTES AND CORRESPONDENCE. 
New Forms of Diatomacee——The following remarks are 
from a paper published by Professor Gregory in the ‘ Trans- 
actions of the Royal Society of Edinburgh,’ on “ New Forms 
of Diatomacez found in the Firth of Clyde and in Loch 
Fine.” For a description of the new species we must refer to 
the paper. 
““TIn two papers read before this Society, I have very fully 
described the Diatomacez of the Glenshira Sand, which is 
very remarkable both for the large number of species found 
in it, which is certainly more than 320, and for the circum- 
stances in which it must have been deposited. There can be 
no doubt, from the nature of the locality, which I have 
lately visited, that this bed was formed in the bottom of the 
Dhu Loch, a shallow fresh-water lake, at that time extending 
about two miles farther up the valley than it now does, and 
being at a higher level. In consequence of a rise in the 
level of the land, or a fall in that of the sea (from which— 
that is, from Loch Fine—the lower end of the lake is sepa- 
rated by a narrow and low barrier, through which the 
waters of the lake pass to Loch Fine), the lake has long ago 
been drained, till its upper end is nearly two miles from the 
point it must have reached when the bed of sand was 
formed. The present level of the lake is considerably lower 
than it was then; the precise difference I had no means of 
ascertaining, but I believe it is about 30 feet. Now, the 
most interesting fact about this lake is, that its actual level 
is that of half-tide, so that at low water the lake is discharged 
into the sea, while at high water the tide flows upward into 
the lake. Hence marine plants and animals are found in 
the Dhu Loch; herring, for example, are often caught in it, 
and were taken while I was in the neighbourhood. Hence 
also the present deposit in the lake exhibits a mixture of 
fresh-water and marine Diatomaceous forms. Now, the 
older sand, the subject of my paper, deposited at a conside- 
rably higher level, also contains both marine and fresh-water 
Diatoms ; and while the individuals of the two classes are 
both abundant, the marine species are at least twice, perhaps 
thrice, as numerous as those of fresh water. 
“The natural, and, I have no doubt, the true explanation 
