5 
On some Undescribed Species of Diatomace^. 
By George Norman_, Esq.^ of Hull. 
(Read November 14th, 1860.) 
(Communicated by T. C. S. Eoper, E.L.S., F.G S, &c.) 
In purposing to give, in this and future short papers, 
figures and descriptions of new forms of Diatomacese from 
my cabinet, I trust that no apology is needed, but rather, by 
so doing, to be of service to diatomists. 
As a general rule, it may not be deemed advisable to 
describe a new form from scanty materials, or from single 
specimens ; but when a form occurs that cannot easily be 
confounded with any described species, the sooner it is made 
known the better, in order that others may have their atten- 
tion drawn to it. 
I gladly make use of this opportunity to call the attention 
of those who have facilities for obtaining from their corre- 
spondents in Australia, the Pacific Islands, West Indies, &c., 
the alimentary matter of Ascidians and other molluscs. It 
will be seen that some of the forms described in this paper are 
irom an Ascidian gathering from the west coast of Australia. 
For this gathering I am indebted to the kindness of Dr. 
J. D. Macdonald, of H.M. Surveying Ship Herald. The 
great bulk of non-diatomaceous matter in this gathering 
being calcareous, it was readily cleaned by means of acid ; 
and turned out to be by far the richest in new and unde- 
scribed forms of any gathering I have had an opportunity 
of examining. 
Among the beautiful forms, are such as Navicula bullata, 
Campylodiscus diplostictus, &c. ; there are a great many which 
I am unable to refer to any existing genera. 
The stomach- contents of the larger Mollusca, such as 
Strombus and Tridacna, would, doubtless, be found to be 
mainly diatomaceous in their nature. 
Even land moUuscs seem to derive part of their nutrition 
from the endochrome contained between the siliceous valves 
of Diatomacese, for on recently examining the fsecal matter 
of our common garden-snail. Helix aspersa, I noticed, among 
other forms, a good many valves of Nitzschia AmphioxySj a 
species which Ehrenberg has found in a great number of 
samples of soil from various parts of the world, and which 
seems to have a wider geographical range than any other 
species that I am acquainted with. 
Again, the tadpole of the common Frog seems to be 
