258 Proceedings of the Royal Irish Academy. 
Smith does not figure the fine marginal strie, and describes the 
marginal triangular bars as if they were moniliform; but with this 
exception his figure is in every respect accurate, so as to remove all 
doubt as to the identity of the species. Walker-Arnott considers that 
Smith’s form is identical with C. minutula, Kiitz., found by him in 
the Luneburg deposit, and adds, ‘‘It is this which Smith obtained 
from the Lough Mourne deposit, but which he has unfortunately 
referred to C. antiqua, a species which does not occur in any of the 
Irish deposits which I have examined.” On Cyclotella, Q.J.M.S., 
Oct., 1860, p. 246. The forms of Cyclotella found on the only slide 
I possess from the Liineburg deposit are those of C. operculata. 
Walker-Arnott evidently had not seen any specimen of C. antiqua, 
for the distinctiveness of the species is too obvious to haye escaped his 
keen observation, had even a single form of it come under his notice. 
Wm. Sm., BoD. Vol. 1., p28 ; Eli. fie. 49... Ralic im obeien., 
p. 812. Rab. Fl. Eur., p. 33. 
Lough Mourne deposit, in which I have occasionally noticed it. 
Sub-peat deposit, Dromore, Strangford Peat, Co. Down. 
Cyclotella rotula, (Kiitz.) Fresh water. 
Valve with a slight depression towards the centre, striz radiate, 
running from the margin to the centre; coarse at the margin, finer 
and finer as they approach the centre, where they appear confused. 
Strie linear, but notched, so as to seem moniliform. (Pl. 26, 
fig. 14.) 
In consequence of supposing that Discoplea rotula of Ehr., Mic., 
T. xxxv. A. xxil., fig. 67, was a species of Cyclotella, Kiitzing, in his 
Species Algarum, changed his original specific name to that of Cyclo- 
tella astreea, and this nomenclature has been adopted by Ralfs and 
Rabenhorst. It is not, however, certain that Ehrenberg’s form pro- 
perly belongs to Cyclotella, and therefore the original name ought to 
be retained. 
Kiitz.. Bae., -p...50,. 1. tis fig.<4. OW. Sm. B.D, Voli pees. 
Pl. v., fig. 50. Walker-Arnott, Q. J. M.58., Oct., 1860, p. 247.—Cy- 
clotella astreea, Ralfs, in Pritch., p. 812. Rab. Fl. Eur., p. 34.—Or- 
thosira rotula, Heiberg, De Danske Diat., p. 32. Cleve, Om Svenska 
och Norska, Diat., p. 217. 
Lough Neagh, in several parts. Lucan, Feather-bed mountain, 
and Grand Canal, Co. Dublin. River Bann, near Coleraine, Co. Derry. 
Lough Mourne and Lough Island-Reavey deposits. Small forms of 
this species may be, at first view, readily mistaken for Cyclotella oper- 
culata, but on close inspection the difference will be obvious. 
Cyclotella papillosa, (N.8.) Fresh water. 
Marginal strie of the valve linear, very fine, central portions 
unstriate and occupied by a circlet of papille, usually five or six in 
number. (Pl. 26, fig. 15.) 
