O74 Proceedings of the Royal Irish Academy. 
figured by Grunow as Navicula scopulorum, in Verhand. der K. K. Zool. 
Bot. Gesell., Band x., 1860, p. 547, T. ii. fig. 6. The present species, 
however, is shorter, broader, and more rhombic; the transverse stric 
more obscure, and not reaching the median line, but leaving a distinct 
intermediate free space. 
Seaweeds, Dalkey Island, Malahide, Co. Dublin. 
(f) Crassinerves. 
‘“« Forms for the most part lanceolate, with very strong median lines 
and very fine scarcely noticeable structure, in which the longitudinal striae 
come out more distinctly than the transverse. These approach the group 
Limose, from which, however, they differ essentially by the colorless condi- 
tion of the valves in a dry state. In the appearance of the median line 
there is an approximation to some forms of the group Cuspidate not to be 
nustaken,”’—Grunow. 
Navicula rhomboides, (Khr.) Fresh water. 
Valve rhomboid; lanceolate; ends slightly rounded; median line 
distinct, with two longitudinal lines close to and nearly parallel with 
it; slightly expanded in the middle, united towards the ends; the 
median line extending slightly beyond the point of junction; striz 
very faint ; length about 0045; breadth about ‘0009. (Plate 31, fig. 49.) 
With a high objective and very skilful illumination the striz are 
found to be parallel. It is noteworthy that in a gathering made by 
me at Lough Awn, on the summit of the Slieveaneiran Mountain, this 
form occurred in abundance, for the most part free, but frequently in 
mucous tubes, ever in single files, and in some cases the frustules were 
placed end to end, without any mucous investment. 
Kitz. Bac., p. 94, T. xxvui., fig. 45; and T. xxx., fig. 44. This 
author attributes the species to Ehrenberg. Wm. Sm., B. D., vol. 1, 
p. 46; Pl. xvi., fig. 129. Rab. Stissw. Diat., p. 38; T. v., fig. 13. This 
figure represents the form as much smaller than it is generally found 
to be. Ralfs, in Pritch., p. 903; Grunow, Verhand. der K. K. Zool. 
Bot. Gesell, Band x., 1860, p. 549. Donkin, N. H. Brit. Diat., p. 42, 
Pl. vi., fig. 11. Schumann, Die Diat. der Hohen Tatra., p. 68. 
Pool, Glencar, near Glengariff, Bantry, Co. Cork.. Lower Lake, 
Killarney, Arraglen, near Castlegregory, Co. Kerry. Friarstown, 
Piperstown, Co. Dublin. River Bann, near Coleraine, Co. Derry. Con- 
nemara, Co. Galway. Rathdrum, Glenchree, Co. Wicklow. Deposit, 
Tollymore Park, Co. Down. . 
Navicula serians, (De Bréb.) Fresh water. 
Valve elliptical-lanceolate ; ends slightly rounded; median line dis- 
tinct, as are also the two longitudinal lines, close to and parallel to the 
