O’Mrara—Report on the Irish Diatomacee. 293 
Found abundantly in a gathering from salt water at Howth, in 
which fresh and marine forms were mingled, the latter greatly pre- 
dominating. Some cuneate forms occurred along with those in a 
normal state, just as described in Smith’s figure; but the former are 
obviously to be regarded as monstrosities. 
Genus VII. Ratrsra, N.G. 
As Diatoma, differing only in this respect, that the valves are 
hyaline, and without costze. 
Ralfsia hyalina, (Kutz.) Marine. 
Valves on front view quadrangular; on side view narrow, nearly 
linear, narrowed at ends. 
Diatoma hyalinum, Kiitz. Bac., p. 47, T. xvii., fig. 20. Wm. Sm., 
BD Volo, pn. 41. PL xt, fic, 312. ° Ralis..in Pritch., ;p. 778,. Pi 
iv., fig. 16. Rab. Fl. Eur., sect. 1, p. 122.—Fragilaria hyalina major, 
Grunow, Verhand der K. K. Zool. Bot. Gesel., Band xu., p. 374.— 
Fragilaria tenerrima, Heiberg, De Danske Diat., p. 63. Cleve, Om 
Svenska och Norska Diat., p. 220. 
Salt ditch, Breaches near Newcastle, Co. Wicklow. Sea-weeds, 
Tramore, Co. Waterford. 
Ralfsia minima, (Ralfs.) Marine. 
Frustules very small; on front view quadrangular; on side view 
broadly elliptical. 
Diatoma minimum, Wm. Sm., B. D., Vol. i., p. 41, Pl. xl, fig. 313. 
Ralfs, in Pritch., p. 778.—Diatoma hyalinum, var. minimum, Rab. 
Fl. Eur., sect. 1, p. 123.,—Fragilaria minima, Grunow, Verhand der 
K. K. Zool. Bot. Gesel., Band xii., 1862, p. 347.-Fragilaria tenerrima, 
Heiberg, De Danske Diat., p. 68. Cleve, Om Svenska och Norska 
Diat., p. 220. 
Found by Ralfs attached to Surirella gemma, but found by me 
in a brackish ditch, Kilkee, Co. Clare, in which no specimen of Suri- 
rella gemma appeared. 
Ralfsia tabellaria, N.S. Marine. 
Frustules very long, :0038 ; on front view regularly quadrangular; 
on side view capitate at the ends; gently decreasing in breadth, and 
then gradually expanding towards the middle. (Pl. 28, fig. 2. ) 
Sea-weeds, Tramore, Co. Waterford. Lough Strangford, Co. 
Down. 
