296 Proceedings of the Royal Irish Academy. 
Rhaphoneis lorenziana, (Grunow.) Marine. 
Valves considerably larger than the last named, and in all respects 
similar, except that in outline the valves are rhomboid. 
Grunow, Verhand, der K. K. Zool. Bot. Gesel., Band xii., 1862, p. 
381, T. iv., fig. 5. 
Piles of wooden bridge, Dollymount, Co. Dublin. 
Rhaphoneis liburnica, (Grunow.) Marine. 
Valves broadly elliptical, almost circular; strie large, moniliform, 
squarish, distinct, larger at the middle, and decreasing in size as they 
approach the margin, radiate; median unstriate, space narrow, ellipti- 
eal. (PL. 28, fig. 5.) 
This form presents very much the appearance of a Cocconeis, in 
which genus I would have provisionally placed it, were it not that 
Grunow, who first discovered it, placed it here. 
Grunow, Verhand der Zool. Bot. Gesel., Band xii., 1862, p. 383, T. 
1 Via 11 Oe 
Arran Islands, Co. Galway. 
Rhaphoneis Harrison, (Wm. Sm.) Fresh water. 
Frustules attached, filamentous, connected by their ends; on front 
view quadrangular; on side view somewhat cruciform ; angles rounded; 
strie costate, slightly radiate ; median unstriate space narrow, linear. 
Odontidium Harrisonu, Wm.8m., B. D., Vol. ii., p. 18, Supp. Pl. lx., 
fiz. 873.—Dimeregramma Harrisonii, Ralfs, in Pritch., p. 290, Pl. vii, 
fig. 6.—Fragilaria Harrison, Rab. Fl. Eur., sect. 1, p. 119.—Diatoma 
Harrisonii, Cleve, Om Svenska och Norska Diat., p. 219. 
Friarstown, Killikee, River Dodder, Bohernabreena, Co. Dublin. 
Royal Canal, near Enfield, Co. Kildare. Portadown. Verner’s 
Bridge, Co. Armagh. 
Genus IX. Sywepra, Ehr. 
Frustules long and narrow, both on side and front view; attached 
by a gelatinous cushion, or by a longer or shorter stipes. 
The characteristics of this genus are so well marked, that very little 
difference of opinion has existed from the first as to the grouping of 
the several species, although the relation of the genus to other genera 
has been very differently represented. Kiitzing includes Synedra in 
his group of Surirellez, in which besides he ranges the genera Campylo- 
discus, Surirella, and Bacillaria. The last named has, indeed, a super- 
ficial resemblance to the frustules of Synedra, but, in consequence of 
its unsymmetrical character, has, by more recent authors, been trans- 
