94 SURFACE DREDGING ON THE DEE. 
the bottle into a test tube; I then fill up with fresh water— 
shake—let the forms settle, pour off the water, and repeat the 
process till all salt is gone ; then drop a portion on a thin glass 
cover, which, placed on a platinum sheet, can be burnt over a 
spirit lamp. This removes all the carbonaceous matter—but do 
not press the burning too much, or you may fuse even silicious 
forms. By this process you get filamentous forms of the 
Diatomacez in their natural position, which is very interesting. 
I will now describe what I found in this dredging :— 
Noctiluca Miliaris. There were a few of these animals, but 
on other occasions in the same locality | have found them 
more abundant. 
The rest of the collection was made up entirely of Diatoms. 
1. Eucampia Zodiacus, W. Sm. Abundant, and in good pre- 
servation. I noticed amongst the Lucampza another form 
which I took to be Britannicus, W. Sm. This has the 
appearance of Zodiacus, but wants the semicircular holes 
which mark that species. 
2. Biddulphia Bailey, W. Sm. Very abundant. This form 
grows in filaments, but is very easily broken up. 
3. Asterionella Bleakleyi, W.Sm. Abundant. This form always 
abundant in the early part of the summer. 
4. Creswellia turris, Grev. Several specimens. This form is 
new in the Estuary of the Dee, and has been seen by few 
observers as a British species. The genus was established 
by Dr. GREvILLE. This diatom was found by Dr. WALKER 
ARNOTT in the Clyde, but had previously been observed by 
the Rev. R. CRESSWELL, when at Teignmouth, in the 
stomach of Cynthia rustica. The frustules are united by 
means of a circle of numerous short terminal processes of 
equal length. In the Dee dredgings I have found as many 
as seven valves of this species connected together. In a 
slide given me by Mr. Harpman from Hong Kong 
Harbour, I have found several varieties of the Creswel/ia—one 
identical with the Dee specimen, the only difference being 
that those from Hong Kong have the silicious covering 
more fully developed, owing probably to their growing 
under more favourable circumstances. This new genus, 
Creswellia, does away with a large number of different 
genera established by Ehrenberg and Kutzing from fossil 
Diatomaceous earths, Dzctyopyxis, Stephanopyxis, Xantho- 
pyxis, &c., &c. 
s Triceratium Brightwellii, Bright. Rare. This curious form 
is remarkable for the great length of the connecting zone, 
which is only very slightly silicious. On account of the 
exceedingly long process at the extremity it would appear 
that this species is nearly connected with Rhzzosolenia. 
