O'Meara — Hcport on the Irish Diatomaceiv. 293 



round abundantly in a gathering fi-om salt water at Howtli, 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 jB.gure ; but the former are 

 obviously to be regarded as monstrosities. 



Genus YII. Ealfsia, IS". Gr. 



As Diatoma, differing only in this respect, that the valves are 

 hyaline, and without costae. 



Ralfsici hyalina, (Kutz.) Marine. 



Yalves 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., 

 B. D., Yol. ii., p. 41, PL xli., fig. 312. EaKs, in Pritch., p. 778, PI. 

 iv., fig. 16. Eab. PL Eur., sect. l,p. 122. — Pragilaria hyalina major, 

 Grunow, Yerhand der K. K. Zool. Bot. Gesel., Band xii., p. 374. — 

 Pragilaria tenerrima, Heiberg, De Danske Diat., p. 63. Cleve, Om 

 Svenska och Norska Diat., p. 220. 



Salt ditch. Breaches near ITewcastle, Co. Wicklow. Sea-weeds, 

 Tramore, Co. "Waterford. 



Balfsia minima, (KaHs.) Marine. 



Prustules very small ; on front view quadrangular ; on side view 

 broadly elliptical. 



Diatoma minimum, "\Ym. Sm., B. D., Yol. ii., p. 41, PL xli., fig. 313. 

 Balfs, in Pritch., p. 778. — ^^Diatoma hyalinum, var. minimum, Eab. 

 PL Eur., sect. 1, p. 123., — Pragilaria minima, Grunow, Yerhand der 

 K. K. Zool. Bot. Gesel., Band xii., 1862, p. 347. — Pragilaria tenerrima, 

 Heiberg, De Danske Diat., p. 63. Cleve, Om Svenska och ISTorska 

 Diat., p. 220. 



Pound by Ealfs 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 iahellaria, IN". S. Marine. 



Prustules 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. 

 DoAvn. 



