394 Proceedings of the Royal Irish Academy. 
Navicula pygmea, (Kiitz..) Marie or brackish water. 
Valve linear, elliptical; marginal band of strize narrow, with a dis- 
tinct ridge on the inner margin; inner band of striz relatively broad, 
reaching the median line, and having a distinct ridge on the outer mar- 
gin; striz fine, linear, nearly parallel; space intermediate between 
the inner and outer bands of striz narrow, lyrate; apparently un- 
striate, but on closer inspection it will be found that the striae which 
seem to be interrupted are really pervious; length about :0015; 
breadth about -00066, but often of much larger dimensions. (Plate 
oo, fie. 7s) 
Wm. Smith (B. D., Vol. 11., p. 91), who attributes the species to 
Kiitzing. Rabenhorst (Stssw. Diat., p. 39) refers to a form under this 
name without a figure; the species is not correctly included among 
those incidental to fresh water. Ralfs, in Pritch., p. 899, who says ‘‘ the 
species occurs in brackish or fresh water;’’ but though oftenfound by me 
in marine gatherings, it never once occurred to me in fresh water. 
Donkin, N. H. Brit. Diat. p. 10, Pl. 1. fig.10. Lagerstedt, Sotvat. 
Diat. frin Spetzbergen och Beeren Eiland, p. 27.—Navicula minutula, 
Wm.5m.,:B. D., Voli.,p: 48; Ply axa. 274: 
Bannow, salt ditch near town of Wexford, River Slaney, near 
Killurin, Tacumshane, Co. Wexford. Malahide, Portmarnock, Piles 
of wooden bridge, Dollymount Strand, Co. Dublin. Galway Bay, 
near town of Galway. Portnacrush, Co. Donegal. Lough Gill, Co. 
Kerry. On seaweeds, Kilkee, Co. Clare. 
Var. cuneata, (O’Meara). Marine. 
Valve linear, elliptical, with cuneate ends; marginal band of strize 
broad; inner band of strie narrow; strie coarse, linear, distant, 
parallel in the middle, shghtly radiate towards the ends, lyrate ; 
free space narrow, and sometimes difficult to detect; length -0017 ; 
breadth -0010. (Plate 33, fig. 8.) 
Stomachs of Ascidians, Broadhaven Bay, Co. Galway. 
(k) Zrifasciate. 
Distinguished by having the intermediate space between the inner mar- 
gins of the marginal bands of strie divided into three distinet longitudinal 
compartments, one about the median line, and one on erther side of the same. 
+ Wot constricted in the middle. 
Navicula expleta. N.S. Marine. 
Valve broadly elliptical; median compartment nearly linear, 
slightly incurved towards the ends, next compartments narrow, 
lunate ; marginal band of striz relatively wide; strie linear, undu- 
late, divided by about five longitudinal sulci; length about -0018 ; 
breadth about :0012. (Plate 338, fig. 9.) 
This form appears to me obviously identical with that described 
