ou) 
36 Proceedings of the Royal Irish Academy. 
another in all respects that, judging from the frustules alone, I am 
disposed to consider that itis not distinct from the present; nor does 
the general appearance of the fronds differ so much as to be irrecon- 
cilable with this impression. 
Haryey’s Mannal, p. 210... Wm: Sm.,.BaD. Vol 1.2479, 2), lee 
fig. 370. Rab. Fl. Eur., sect. 1., p. 273—Schizonema scoparium, 
Kiitz. Bac., p. 114, T. xxvu., fig. 1—Micromega laciniatum, Ralfs, 
in Pritch.,p. 932. 
Carrickfergus to Antrim, collected by Dr. David Moore. Galway, 
collected by M‘Calla. 
Schizonema gracillimum, (Wm. Sm.) Marine. 
‘‘ Frond capillary, simple below ; sparingly branched and sub-mem- 
branous towards the apices. Frustules crowded in irregular files. 
Valves elliptico-lanceolate. Length of frustule .0009, breadth of valve 
00015.” —Wm. Smith. Striz linear, very slightly radiate. Frustule on 
front view narrow, quadrangular. So far as the frustules are concerned, 
in outline and general appearance the species differs little from Schi- 
zonema parasiticum. The striz may be a little coarser and the valve 
somewhat narrower. 
Wm. Smith, B. D., Vol. ii., p. 79, Pl. lix., fig. 372.—Micromega 
eracillimum, Ralfs, in Pritch., p. 934. 
Nannywater, Laytown, Co. Meath. 
(ttt). Frustules without strie. 
Schizonema obtusum, (Grev.) Marine. 
“Frond filiform, sparingly branched, apices abrupt. Frustules 
exceedingly numerous, in irregular files; valves elliptical. Length of 
frond 1”; length of frustule -0011; breadth of valve 00025.” Wm. 
Smith. To which should be added that the valves are rounded at the 
ends. S(P1229) fie" 20-) 
Greville, Brit. Fl., p. 418. Harvey’s Manual, p. 209. Rab. FI. 
Eur., sect. 1, p. 272.—Micromega obtusum, Ralfs, in Pritch., p. 931. 
Near Dunluce Castle, Portballintrae, Co. Antrim, collected by 
Dr. David Moore. Merrion, Malahide, Co. Dublin. Galway. 
Schizonema dilwynti, (Agardh.) Marine. 
‘‘Frond capillary throughout, sparingly branched, tenacious; apices. 
acute. Frustules exceedingly crowded towards the apices, scattered and 
remote in the older portions. Valves lanceolate, acute. Length of frond 
2” to 5”, or upwards ; length of frustule -0008 ;. breadth of valve -0002.” 
Wm. Smith. So far as the frustules are concerned there is but little 
difference between this and the preceding species; the only difference 
