282 Proceedings of the Royal Irish Academy. 
united in filaments, in which they are parallel; connecting zone usually 
very narrow ; striz on the side view very fine, usually persistent, and 
appearing on the front view, where they form a narrow margin. 
Fragilaria capucina, (Desmazieres.) Fresh water. 
Frustules flat, so that the band of striz appearing on the front 
view is very narrow. On side view the valves are narrow, linear, 
with either acute or slightly rounded apices; striz very fine, per- 
sistent. 
This species includes Fragilaria acuta, which is scarcely distin- 
guishable from it. 
Kiitz. Bac., p. 45, T. xvi., fig. 3. Rab. Stiissw. Diat., p. 33; T.1., 
fig, 2., .Wm..5m.,.B.D;, Vol. 115;p.22,)Plixxxy.,; fie; 2062) ale am 
Pritch., p. 776. Grunow, Verhand der K. K. Zool. Bot. Gesel., Band 
xil., 1862, p. 372. Castracane, Catalogo di Diat. raccolte nella Val. 
Intrasca, p. 15. 
This species is of almost universal occurrence. 
Fragilaria virescens, (Ralfs.) Fresh water. 
Frustules more arched than in the preceding species, and the 
marginal line of striw, as seen on the front view, therefore wider. 
On side view linear, or slightly elliptical; narrowed at the ends, but 
not constricted ; stric fine, persistent. 
Ralfs, A. N..H3, -Yol. xii. Plan, fig. 6... Kitz; Baes, p246, 0 xvi, 
fie. 4... Rab. Sussw. Diati, p. 33; T. 1., fig. 1. ..Wm. Sm. 'B. D7 Vole 
p. 22, Pl. xxxv., fig. 297. Ralfs, in Pritch., p. 777. Grunow, Verhand 
der K. K. Zool. Bot. Gesel., Band xu., 1862, p. 373, T. iv., fig. 15. 
Heiberg, De Danske Diat., p.60. Castracane, Catalogo di Diat. raccolte 
nella Val. Intrasca, p. 15. Cleve, Om Svenska och Norska Diat., 
p. 219. 
Friarstown, Piperstown, Kilhikee, Co. Dublin. Glenchree, Greenane, 
Co. Wicklow. Feighcullen, Co. Kildare. (Moanarone, Co. Cork; Wm. 
Sm.) 
Fragilaria equalis, (Heiberg.) Fresh or Brackish water. 
Frustules considerably longer than in the last species; on side view 
linear; ends attenuated and rounded ; strie fine, persistent. Heiberg’s 
figure represents the striz as interrupted by a narrow median space, 
but in the forms that came under my inspection the striz, although at 
first they seemed interrupted, 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 Norska Diat., p. 219. 
Oyster beds, Malahide, Co. Dublin. ae 
