On some Undescribed Species of Diatomace^e. 

 By George Norman, Esq., of Hull. 



(Eead November 14th, 1860.) 

 (Communicated by F. C. S. Roper, E.L.S., F.G S., &c.) 



In purposing to give, in this and future short papers, 

 figures and descriptions of new forms of Diatomaceae 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 

 from 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 molluscs 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 Amphioxys, a 

 species which Elu-enberg has found in a great number of 

 samples of soil fi'om 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 



