306 Proceedings of the Royal Irish Academy. 
Var. longiceps, (Ehr.) Fresh water. 
Like the preceding, but longer, more slender, the ends not so 
large; not-triangular, but rounded off. (Pl. 28, fig. 23.) 
Synedra longiceps, Rab. Siissw. Diat., p. 55. Ralfs, in Pritch., 
p- 788. Grunow, Verhand. der K. K. Zool. Bot. Gesel. Band xi.., 
1862, p. 386.—Synedra notarisii, Castracane, Dialogo di Diat. raccolte 
nell Val. Intrasca, p. 9. 
Twyford Lough, near Athlone, Co. Westmeath, unmixed with the 
former, and mixed with it in ditch near railway station, Dundalk, Co. 
Louth. 
Synedra ulna, (Ehr.) Fresh water. 
Frustules on front view linear ; on side view linear, suddenly con- 
tracted at the ends, which are slightly constricted and rounded; stric 
interrupted in the centre by a quadrangular vacant space. (Pl. 28, 
fig. 24.) 
It is not easy to comprehend how Smith could have regarded as 
one species the two forms described by him under this name, B. D., 
Vol.i., p. 71, Pl. xi., figs. 90 and 90 B, than which no two forms of 
the genus seem to be more distinct. The result is, that great confu- 
sion has been introduced, which may be dispelled by a careful com- 
parison of Kiitzing’s description and figure of the species with the 
actual forms. It is questionable whether the form figured by Smith, 
as above, fig. 90 B, really belongs to Synedra ulna; but, unqestion- 
ably, that of fig. 90 must be excluded from its limits. 
Kutz. Bac.,. p, 66, To xxx., fig::28. Rab. Stissw. Diat. p04, 
T. iv., fig.4. Ralfs, in Pritch., p. 788, Pl. x., fig. 184, in which only 
the front view is given, and the mode of growth is on a short stipes, 
and scattered. Grunow, Verhand. der K. K. Zool. Bot., Gesel. Band 
Xl., 1862, p. 397, where he identifies this species with Smith’s fig. 90B, 
as above cited, and makes fig. 90 a variety marked by the name of 
lanceolata. Heiberg refers to the species as identical with that of 
Smith’s fig. 90; De Danske Diat., p. 64. Rabenhorst Fl. Eur., sect. 1, 
p- 183, does not refer to Smith’s figures, and follows Grunow, only 
that he includes Synedra salina, a very distinct species, as a variety of 
Synedra ulna. Castracane identifies the form so named with that of 
Rabenhorst Siissw. Diat., T. iv., fig. 4, as well as with that of Smith, 
fig. 90. Catalogo di Diat. raccolte nell Vall. Intrasca, p. 10. 
Tacumshane, Co. Wexford. Caum Lough, near Tralee, Glencar, 
Co. Kerry. River Dodder, Co.Dublin. Ditchnear Wicklow. Feigh- 
cullen, Maynooth, Co. Kildare. River Moy, Foxford, Co. Mayo. 
Well, Farraghy, Co. Cork. © 
Var. oxyrhynchus, (Kitz.) Fresh water. 
Much longer than the typical species, and ends on side view 
sharper. (Pl. 28, fig. 25.) 
Kutz. Bac., p. 66, T. xiv fies, 1L.)Ralis,an Prich. ep ages- 
