O’Mrara—Report on the Irish Diatomacee. 301 
avoid confusion, the specific name adopted by Ehrenberg and Kiitzing 
for this species had best be abandoned, and the designation proposed 
by Grunow as above substituted for it. 
Raphoe, Co. Donegal. Lough Neagh, near Lurgan, Co. Armagh. 
Sub-peat deposit, Dromore, Co. Down. 
Navicula bacillum, (Ehr.) Fresh water. 
Valves linear; ends rounded; costz fine, strongly marked in the 
middle, radiate ; intermediate free space narrow, slightly expanded in 
the middle; length about *0018, breadth about -0005. (Plate 30, 
fig. 29.) 
Ehrenberg has given many figures of a species so named, some of 
which are utterly undistinguishable ; one from a marine habitat in- 
dicated cannot be the same. Two, however, of his figures are plain 
enough for satisfactory identification. 
Bbrs Mie. T..xy., Aefie. 38; T. u.; 2. fie, 14... Kitz, Bac.,. -p: 96, 
fT. sev. fie.69. Wm. Sm-, B-).;Vol.i., p- 91... Balis, im Pritch., 
p- 907. Grunow, Verhand. der K. K. Zool. Bot. Gesell., Band x., 
1860, p. 551, T. iv., fig.1., Rab. Stissw. Diat., p. 39; T. vi., fig.-76. 
Heiberg, De Danske Diat., p. 85. 
Ditch near town of Wexford. Lower Lake, Killarney, Co. Kerry. 
Lough Neagh, near Lurgan, Co. Armagh. Cushendun, Co. Antrim. 
Derrylane Lough, Co. Cavan. Sub-peat deposit, Dromore, Co. Down. 
Lough Mourne deposit. 
Navicula americana, (Ehr.) Fresh water. 
Valve linear, oblong, with rounded ends; length ‘0035, breadth 
-0010; slightly constricted; coste fine, convergent in the middle, and 
nearly parallel towards the ends; intermediate free space wide, greatly 
expanded in the middle; central nodule large, median line very 
strongly marked. (Plate 30, fig. 30.) 
Ehr. Mic. T. I1., a, fig. 16. Kitton, Science Gossip, June, 1868, 
p. 1381. 
This species in a fossil state is widely dispersed; besides the 
locality indicated by Ehrenberg, it has been found by Mr. Kitton of 
Norwich, in Perley’s Meadow deposit, Sth. Bridgton, Maine, U. 8S. A. 
I found it in great abundance in a fresh water deposit discovered by 
Dr. Moss, R. N., in Vancouver’s Island, as also in a sub-peat deposit 
from Dromoze, Co. Down. Rev. George Davidson has furnished me 
with specimens found in a fossil state in Lough Canmore, near Aber- 
deen. I have found it in tolerable abundance in a living state in 
Lough Neagh, near Lurgan, Co. Armagh. 
Navicula isocephala, (Ehr.) Fresh water. 
Valve long, narrow; length -0055, breadth 0007; undulate on the 
margin, with three nearly equal and slight inflations; ends constricted 
