TRANSACTIONS. 
Remarks on some DiatomacetE, new or imperfectly de- 
scribed^ and a new Desmid. By Tuffen West^ F.L.S. 
The object of tlie present remarks is to bring before the 
members of tlie Microscopical Society some two or three 
Algae with which I have been favoured by the kindness of 
correspondents ; I shall also add a few particulars to the 
descriptions of forms already known^ and shall suggest some 
corrections in the published notices of others. 
In working over numerous slides of Diatomace8e_, belonging 
to Mr. T. Brightwell^ of Norwich, I made sketches of the 
following Triceratia, which were reserved till such time as 
sufficient material had accumulated for another of his valuable 
papers on this genus. Being unable to continue his labours 
in this field, he has cordially acceded to the request that I 
might be permitted to publish them for him. 
1. Triceratium. 
T. parmula, Br. Four-sided variety. (PI. VII, fig. 1.) 
With the instances now known of variation in the number 
of sides in species belonging to this genus, accumulated by 
Mr. Brightwell, Dr. Wallich, and others, little room can 
remain for the doubt expressed by the late Professor Bailey, 
as to the possibility of such an occurrence. The specimen 
figured occurred in a gathering from the Mauritius. 
T. venosum, Br. (Fig. 2.) 
Angles slightly elevated above the general surface of the 
valve, not produced into horns, truncate ; puncta and cana- 
liculi not reaching the apposed edges of the valves, but 
leaving a broad hyaline margin, free from markings of any 
kind ; cingulum ? 
T. castellatum, n. sp. (Fig. 3.) 
Sides of the frustule deeply concave, separated by siliceous 
lines from the central portion ; angles forming segments of 
circles. On front view the angles form dome-shaped emi- 
voL. viii. q 
