474 PROFESSOR GREGORY ON 
banks of the Firth of Clyde, the level of which must always have regulated that 
of Loch Fine since the present form of the coast has existed. 
There was, however, a circumstance which at first tended to throw some 
doubt on this conclusion, according to which the marine forms of the Glenshira 
sand must have come from Loch Fine. For although the known and described ma- 
rine Diatoms found in the sand occur on our coasts, yet I was struck with the fact 
that out of upwards of fifty new or undescribed forms, there seemed to be no 
trace in deposits from the Firth of Clyde, examined by more than one naturalist 
during the progress of my investigation. The fact of these forms being unde- 
scribed was prima facie evidence that they had not yet occurred on the British 
coasts. 
Yet it was evident that the formation of the Glenshira sand was, geologically 
speaking, very recent ; so recent, indeed, that we could not suppose any number 
of species to have since become extinct. I came, accordingly, to the conclusion, 
that these undescribed forms must still exist in the waters of Loch Fine, or, what 
is the same thing, of the Firth of Clyde. I was therefore desirous to examine 
with care deposits from these waters, and this, during the past six months, I 
have been enabled fully to do. 
The materials which I have examined are the following :— 
1. A small quantity of dirt or sand washed from some nests of Lima hians, 
dredged in Lamlash Bay on the 19th of July last, in 4 fathoms, by Professor 
AutMAN. This material, though, when cleaned, very scanty, proved the richest 
of all. 
2. Four dredgings, made by myself, with the kind assistance of the DuxKrE of 
ARGYLL, in Loch Fine, at different points within two or three miles of Inveraray. 
These were all different, and three of them were interesting. They were taken at 
depths of from 14 to 18 fathoms, early in October last. 
3. Three dredgings made at the same time by the Rev. Dr Barctay, in Loch 
Fine, off Strachur, at depths of 15, 20, and 60 fathoms, also in October last. 
4. Three materials forwarded to me in October by the Rev. Mr Mixes of Glas- 
gow, who was for some time on the Holy Island, in Lamlash Bay. 
One of these was washed from the nests of Zima,hians, as I had reported the 
richness of the former. These last were from 7 fathoms in Lamlash Bay, This 
material, dredged, I think, in June, was not so rich in Diatoms as Professor ALL- 
MAN’S, but yet contained many interesting forms. 
The second was a coarse red sand, dredged off Invercloy, Arran, which was 
rather poor. 
The third was a mass of Corallina officinalis, taken with the hand, in rocky 
pools, at Corregills, Arran, when the tide was low. The Corallina proved to have 
been a good Diatom trap, and yielded a material, not remarkable for the number 
