O’Mrara—Report on the Irish Diatomacee. 307 
Grunow makes Synedra oxyrhynchus a distinct species, which he iden- 
tifies with Synedra oxyrhynchus, Wm. Sm., B.D., Vol.i., p. 71, 
Pl. xi., fig. 91, and figures a variety distinguished as amphicephala, 
which appears identical with Synedra ulna, Wm. Sm., B. D., Vol. 1., 
p. 71, Pl. xi., fig. 90 B. The form under consideration seems diffe- 
rent from both. Rab. Fl. Eur., sect. 1, p. 185, who follows Grunow. 
River Dodder, near Dublin. River Moy, Foxford, Co. Mayo. 
Var. amphirhynchus. Ehr. Fresh water. 
Like the typical species, from which it differs chiefly by the ab- 
sence of the quadrangular unstriate space in the centre of the valve, 
on side view. (PI. 28, fig. 26.) 
Kutz. Bac., p. 66, T. xiv., fig. 15. Rab. Siissw. Diat., p. 55, 
T. iv., fig. 7. Ralfs, in Pritch., p. 788. Grunow, Verhand. der K. K. 
Zool. Bot., Gesel., Band xu1., 1862, p. 397. 
River Moy, Foxford, Co. Mayo. Bohernabreena, River Dodder, 
pond, Botanic Gardens of Trinity College, Co. Dublin. Greenane, 
Kilcool, Powerscourt, Co. Wicklow. Feighcullen, Co. Kildare. LKiulle- 
shin, Queen’s County. Well, Farraghy, Co. Cork. Stream near Giants’ 
Causeway, Co. Antrim. 
Mr, Kitton of Norwich, and Rev. George Davidson, have supplied 
me with specimens which would appear to belong to this variety, but 
. growing in short filaments, after the manner characteristic of Fragi- 
laria. I find no description of the stipes in any of the authors who 
have referred to this form, nor have I ever seen it myself in setu; but 
not unfrequently have I noticed it aggregated in tablets, but not 
parallel at the ends, as if the aggregation were accidental. 
Synedra longissima, (Wm. Sm.) Fresh water. 
Frustules very long on front view, quadrangular; on side view li- 
near, till near the ends, towards which it is almost imperceptibly 
attenuated ; ends constricted and then dilated, without any central 
free space ; valves sometimes slightly arcuate. (Pl. 28, fig. 27.) 
Smith’s description of this species is tolerably accurate; but the 
figure, B.D., Vol.i., Pl. xii., fig. 95, is calculated to mislead. The 
form possesses no median line, nor is there a central free space, such 
as this figure represents. 
Wm. Sm., 5B. D., Vol.-i., p..72.,, Ralfs, in; Pritch., p.786, who 
asks ‘‘is this distinct from Synedra biceps?” to which I reply, cer- 
tainly it is. The forms differ greatly in their general appearance, 
and may be discriminated by the fact that the strie in Synedra bi- 
ceps are pervious—in Synedra longissima they are separated by a 
median sulcus. Cleve, Om Svenska och Norska Diat., 220. Rab. 
Fl. Eur., sect 1, p. 180, who remarks that ‘it appears to him an 
elongated, gently-undulate form of Synedra biceps,” and strangely 
