282 Proceedings of tJie Royal Irish Academy. 



united in filaments, in vhicli they are parallel ; connecting zone usually 

 Tery narro-w ; striae on the side view very fine, usually persistent, and 

 appearing on the front vie"vr, wliere they form a narrow margin. 



Fragilaria capucina, (Desmazieres.) Freshwater. 



Frustules flat, so that the band of striee appealing on the front 

 view is very narrow. On side view the valves are narrow, linear, 

 with either acute or slightly rounded apices ; strise very fine, per- 

 sistent. 



This species includes Fragilaria acuta, which is scarcely distin- 

 guishable from it. 



Kutz. Bac, p. 45, T. xvi., fig. 3. Eab. Siissw. Diat., p. 33 ; T. i., 

 fig. 2. Vm. Sm., B.D., Yol. ii, p. 22, PI. sxxv., fig. 296. Ealfs, in 

 Pritch., p. 776. Granow, Yerhand der K. K. Zool. Pot. Gesel., Band 

 xii., 1862, p. 372. Castracane, Catalogo di Diat. raccolte nella Yal. 

 Intrasca, p. 15. 



This species is of almost universal occurrence. 



Fragilaria virescens, (Ealfs.) Fresh water. 



Frustules more arched than in the preceding species, and the 

 marginal line of striae, as seen on the front view, therefore wider. 

 On side view linear, or slightly elliptical ; narrowed at the ends, but 

 not constricted ; striae fine, persistent. 



Ealfs, A. :N'. H., Yol. xii., PL ii., fig. 6. Kiitz. Bac, p. 46, T. xvi,, 

 fig. 4. Eab. Siissw. Diat., p. 33, T. i., fig. 1. ^m. Sm. B. D., Yol. ii, 

 p. 22, PL XXXV., fig. 297. Ealfs, in Pritch., p. 777. Grunow, Yerhand 

 •der K. X. Zool. Bot. Gesel., Band xii., 1862, p. 373, T. iv., fig. 15. 

 Heiberg, De Danske Diat., p. 60. Castracane, Catalogo di Diat. raccolte 

 nella Yal. Intrasca, p. 15. Cleve, Om Svenska och Xorska Diat.. 

 p. 219. 



Friarstown, Piperstown, Killikee, Co. Dublin. Glenchrce, Greenane, 

 Co. Wicklow. Feighcullen, Co. Eildare. (^Moanaxone, Co. Cork; Wm. 

 Sm.) 



Fragilaria cequaiis, (Heiberg.) Fresh or Brackish water. 



Frustules considerably longer than in the last species ; on side view 

 linear ; ends attenuated and rounded ; striae fine, persistent. Heiberg's 

 figure represents the striae as intennipted by a naiTOw median space, 

 but in the forms that came under my inspection the striae, although at 

 first they seemed inten-upted, as described by Heiberg, on closer ex- 

 amination were obviously persistent. 



Heiberg, De Danske Diat., p. 61, T. iv., fig. 12. Cleve, Om 

 Svenska och Xorska Diat., p. 219. 



Oyster beds, Malahidc, Co. Dublin. 



