4 
308 Proceedings of the Royal Irish Academy. 
adds, that ‘‘ he considers Grunow has rightly regarded it as a variety 
of Synedra splendens.””—Synedra splendens, var. longissima, Grunow, 
Verhand. der. K. K. Zool. Bot. Gesel., Band xii., 1862, p. 897. Grunow 
considers this form identical with Synedia biceps, Kiitz. Bac., p. 66, 
T. xiv., figs. 18 and 21, and Rab. Siissw. Diat., p. 55, T. v., fig. 9. 
But however this may be, Synedra longissima and Synedra biceps are 
in reality distinct species. 
Pond in Botanic Gardens, Belfast. Malahide. St Fenton’s Well, 
Sutton. Streamlet, Newcastle Lyons, Co. Dublin. Twyford Lake, 
near Athlone, Lake Belvidere, Co. Westmeath. Ditch near railway 
station, Dundalk, Co. Louth. Ditch near Wicklow. | 
Synedra obtusa, (Wm. Sm.) Fresh water. 
Similar to the preceding species, but much shorter; not so muck 
constricted or expanded at the rounded ends. (PI. 28, fig. 28.) 
Wm. Sm., B. D.; Vol. i., p. 71, Pl. xi., fig. 92, who-reeards-it as 
= Synedra ulna, Ehr. Inf., T. xvii., fig. 1; but of this he is doubtful; 
and Synedra equalis, Kitz. Sp. Alg., p. 45, ad speciem que dedit 
amico De Brébisson. If Synedra equalis, Kiitz., just referred to, be 
the same as that described by the same author, Bac., p. 66, T. xiv... 
fig. 14, it is scarcely identical with the present species.—Synedra 
splendens, var. obtusa, Grunow, Verhand. der K. K. Zool. Bot. 
Gesel., Band xii., 1862, p. 897.—Synedra splendens, var. sequalis, 
Rab. Fl. Eur., sect. 1, p.1384. The linear form of the side view 
appears to me to distinguish this from the form named Synedra splen- 
dens by both the authors last referred to, which Grunow describes as 
generally, small lanceolate, and less frequently linear, and Rabenhorst 
as linear, lanceolate. If this form can be regarded as a variety of any 
other, I think it should be of Synedra longissima, which it very closely 
resembles. 
Tacumshane, Co. Wexford ; Ditch near railway station, London- 
derry. Limestone quarry, Mullingar. Twyford Lake, near Athlone. 
Lake Belvidere, Co. Westmeath. 
(e). Strie interrupted by a narrow, longitudinal sulcus ; valves, narrow 
elliptical. ! 
Synedra splendens, (Kiitz.) Fresh water. 
Frustules long: on front view usually wider at the ends than in 
the middle ; on side view, narrow elliptical, gradually attenuated to- 
the slightly capitate ends. (Pl. 28, fig. 29). . 
I have found it impossible to discriminate between this species: 
and Synedra ulna, as described by Wm. Sm., B.D., Vol. i., p. 71, 
Pl. xi., fig. 90. The latter species, as described by Kiitzing Bac..,. 
p. 66, T. xxxx., fig. 28., is on side view perfectly linear; and 
although I have occasionally seen specimens which exhibit a ten- 
