NEW FORMS OF MARINE DIATOMACER. 533 
is mixed with S. wndulata; and I know of no distinction beyond that of the ab- 
sence of undulations on the margin, unless it be that the striz in S. Hennedyana 
are perhaps a little finer than in S. undulata. Even of this I am not sure. 
But the figures, which are very accurate, will enable the reader to form his own 
conclusions. 
Such are the results obtained, up to this time, by the examination of these 
11 gatherings from the Firth of Clyde and Loch Fine, 10 of which are true dredg- 
ings, while the 11th is derived from Corallina officinalis, to which a good many 
Diatoms have adhered. 
From the remarkable analogy between the Glenshira Sand and these gather- 
ings, we may regard it simply as another dredging, the marine forms in which 
have been derived from Loch Fine. I have shown that the period at which it 
was deposited has not caused any material difference of composition, and that we 
may say, in general, that it does not differ more from the recent dredgings than 
they do from each other. 
Considering, then, all as supplying us with existing forms, we are struck with 
the unexpectedly large number of undescribed species which this exploration of 
the waters of the Clyde, though very limited in the area whence the materials 
were derived, has yielded in a short space of time. 
It is worthy of notice, that the great majority of these new forms are not 
only new as British species, but have not been observed elsewhere, although 
EsRENBERG and Barey have both described many rich marine gatherings from 
different parts of the world. 
This proves that the existing stores of marine Diatoms have not yet been by 
any means fully explored. It is therefore highly desirable that dredgings or 
soundings from all seas and estuaries, and from every part of them, should be 
procured and carefully searched. From what has been already recorded, as well 
as from the results here given, it appears that estuaries and harbours, or other 
localities near the coast, are likely to be the richest in Diatoms, perhaps from the 
comparative shallowness of the water. But the conditions of the distribution 
of these organisms in the sea, and of the accumulation of their indestructible si- 
‘liceous shells, are not yet known with certainty. Thus, while every one of these 
Clyde dredgings proved more or less rich in Diatoms, I have found several from 
the Long Narrows, in the Firth of Forth, kindly given me by Dr Hecror, to be 
very poor in comparison, and indeed not worth the trouble of mounting. And 
while Baitey has found many interesting forms of this class in soundings from a 
depth of 1700 fathoms, and even of 2700 fathoms, in the Kamtschatka Sea, a num- 
ber of Atlantic soundings, from depths varying from 85 to 2000 fathoms, which, 
by the kindness of Professors W. THomson and ALLEN THomson, I was allowed to 
see, contain indeed Foraminifera and Polycystinez, but are almost entirely desti- 
tute of Diatomaceee. Yet Baitey has found Diatoms in Atlantic soundings from 
_ VOL. XXI. PART Iv. 7D 
