O’Mrara—Report on the Irish Diatomacee. 375 
same; transverse strie obscure, slightly oblique ; longitudinal striz dis- 
tinct ; length about -0088 ; breadth about :0009. (Plate 31, fig. 50.) 
Kiitz. Baor, pw 2c exes, figs '235 Te axvin., fie: 43. This 
author considers the species identical with Frustulia ser ians, De Brébis- 
son, and with Navicula lineolata, Ehr. He adds, ‘‘ I have no doubt 
that the Ehrenbergian form, which has been described in our T. xxviii., 
fig. 48, according to Ehrenberg, is perfectly identical with that of De 
Brébisson.”” That form is rather smaller than Navicula serians, and 
therefore some doubt may reasonably be entertained on the subject. 
It seems better then, with Donkin, to attribute the species to De Brée- 
bisson than to abandon the specific name by which the species has been 
so long known. Wm. Sm., B. D., vol. i., p. 47, Pl. 16, fig. 130. 
Rab. Siissw. Diat., p. 38; T. vi., fig. 51; Ralfs, in Pritch., p. 904. 
Grunow, Verhand. der K. K. Zool. Bot. Gesell, Band x., 1860, p. 549 ; 
be ee fig. 13. Cleve, Om Svenska och Norska Diat., p. 228. Don- 
kin, N. i. Brit. Diat., p. 41, Pl. vi., fig. 10. 
Pool, Cushendun, Co. Antrim. Piperstown, Co. Dublin. Glen- 
chree, Co. Wicklow. Pool near town of Wicklow. Tollymore Park 
deposit, Co. Down. 
Navicula crassinervia, (De Bréb.) Fresh water. 
Valve small, elliptical-lanceolate ; ends produced and slightly con- 
stricted ; longitudinal sulci parallel to the median line, distinct; strice 
obsolete; length about :0024; breadth about -0005. (Plate 31, fig. 51.) 
Wines, bo. Volt. p. 47, Sippy kl: xxxi., fie: 271, who 
describes and figures the species according to specimens furnished by 
‘De Brébisson. Ralfs, in Pritch., p. 900. Grunow, Verhand. der K. K. 
Zool. Bot. Gesell., Band x., 1860, p. 548, T. v., fig. 12. Cleve, Om 
Svenska och Norska Diat., p. 228. Donkin, N. H. Brit. Diat., p. 42, 
Pl. vi., fig. 12. This last named author considers this species identical 
with Frustulia saxonica, Rab. Fl. Eur. Alg., sect. i., p. 227. 
Friarstown, Piperstown, Featherbed Mountain, Co. Dublin. Lough 
Gill, Co. Kerry. Bantry, Co. Cork. Rostrevor, Co. ave Rath- 
drum, Glencree, Co. Wicklow. 
Nawicula dirhynchus, (Ehr.) Fresh water. 
Valve nearly linear, narrow; ends produced, and slightly capitate. 
Longitudinal sulci parallel with median line, distinct. Transverse 
strie obsolete; longitudinal strie distinct; length, ‘0022, breadth, 
"0005. (Plate 31, fig. 52.) 
Kitzing, Bac., p. 95, T. xxviil., fig. 48, by whom the species is 
attributed to Ehrenberg. Rab. Siissw. Diat., p. 40, T. vi., fig. 48. 
Ralfs, in Pritch., p. 901." Donkin, N. H. Brit. Diat., p. 29, Pl. v., 
fig. 3. The last named author remarks that ‘‘in outline this species 
has a strong resemblance to Navicula affinis, but it is much smaller, 
