O’Mrara—Report on the Irish Diatomacee. 337 
being that while in the former case the valve is rounded at the ends, in 
the present case they are acute. I have sometimes found both species 
in the one gathering. 
Agardh. Syst., p. 10. Id. Consp., p. 20. Grev. Brit. Fl., p. 412. 
Harvey’s Manual, p. 212. Kiutz., Bac., p.118, T. xxvi., fig. 3. Wm. 
Sm., B. D., Vol. u1., p. 77, Pl. lviu., fig. 366. Ralfs, in Pritch., p. 928. 
Rab., Fl. Eur., seet..1, p. 272. 
Rathlin Island, Carrickfergus, Carnlough Bay, Co. Antrim—all 
collected by Dr. David Moore. River Nannywater, Laytown, Co, Meath. 
Merrion, Co. Dublin. 
(b). Achlamydie. Frustules without a gelatinous investment. 
Genus VI. Drapesmis, Kiitz. 
Frustules united in a filament. 
Diadesmis williamsonit,(Wm.Sm.) Marine. 
On front view margins of frustules undulate, and exhibiting the 
striation of the valve; on side view, valve linear, acuminate at the 
ends. Strie moniliform. (Pl. 29, fig. 21.) 
This form was first partially described by Wm. Smith, B. D., Vol. 
ii., p. 14, Pl. xxxiii., fig. 287, who, having seen only the front view 
so accurately figured by him, doubtfully referred it to the genus 
~ Himantidium. Subsequently Gregory, who had opportunity of more 
thoroughly investigating it, transferred it to the genus Diadesmis, to 
which it properly belongs. Grunow refers this species to the genus 
Dimeregramma, and makes the following observations :—‘‘ Of the 
EKunotia-like structure of the same there is no question; the margins 
of the front view are never so distinctly triundulate as in Smith’s 
description ; for the most part the middlemost elevation is found much 
stronger than the other two, in consequence of which it approaches 
Dimeregramma minor.’’—Verhand. der K. K., Zool. Bot. Gesel., Band 
xil., 1862, p. 377. 
Gregory, Diat. of Clyde, p. 25, Pl. x., fig. 40, in which both side 
and front views are accurately delineated. Ralfs, in Pritch, p. 923. 
Rab. Fl. Eur., sect. 1, p. 260. 
From stomachs of Ascidians, Roundstone Bay, Co. Galway. 
Genus VII. Bresissonra, Grunow. 
Frustules simple, stipitate. 
The only species of this genus was by Smith described and figured 
under the name of Doryphora Boeckii. The genus Doryphora had 
