404 Proceedings of the Royal Trish Academy. 
Navicula incisa, N.S. Marine. 
Valve deeply constricted ; median compartment narrow; inflexed 
at ends, shghtly contracted in the middle; compartments at either 
side narrow, striate; strie faint; marginal band of strie narrow in 
the middle, wide towards the middle of the lobes; striae convergent 
in the middle, nearly parallel for some distance, and slightly radiate 
towards the ends; costate, divided into four distinct equal bands, by 
three deep sulci, which lie conformably with the outer margin; the 
coste in each band appear slightly curved; length 0035, breadth 
0015 ; breadth at the constriction ‘0010. (Plate 33, fig. 33.) 
This form somewhat resembles that figured by Schmidt, Atlas der 
Diat., T. xii., figs. 21 to 24, without a name, and which he thinks 
stands between Navicula apis and Navicula splendida, but I doubt 
its identity with either. 
Arran Islands, Co. Galway. 
Navicula crabro, (Ehr.) Marine. 
Valves large, slightly constricted ; median compartment narrow, 
slightly inflexed at ends, constricted in the middle; compartments on 
either side wider, gently tapering towards the ends; striate, the ends 
of the strie appearing as large puncta on the elevated margin of the 
inner edge; marginal striate band wide; strize convergent in the 
middle, radiate towards the ends; costate; length -0073, breadth 
"0021; breadth at constriction ‘0015. 
Wm. Sm., B. D., Vol. n., p. 94. Donkin, IN. HH? Brit oie 
p. 46, Pl. vii., fig. la. Ralfs, in Pritch., p. 894. Rab. FI. Eur. Alg., 
sect. 1., p. 204.—Diploneis crabro, Ehr.,. Mic., T. xix:, fig? 29. 
Navicula pandura, De Brébisson, Diat. du Littoral de Cherbourg, 
p. 16, Pl.i., fig. 4—Pinnularia pandura, var. elongata, Gregory, Diat. 
of Clyde, p. 489, Pl. ix., fig. 22. Though Ralfs and Rabenhorst seem 
to regard this form as distinct from Navicula pandura, I am inclined 
to think with Donkin, that there is no distinction between them. 
Smith describes the striz as obscurely moniliform ; but all the figures I 
have seen represent the striz as distinctly costate, and such I consider 
is their normal character. Donkin’s figure represents the compart- 
ments at either side of the median compartment as unstriate, except 
on the inner edge, where there is a row of large bead-like detached 
puncta. In all the specimens I have seen, the coste in this portion, 
though of a fainter colour, are clearly traceable all through; the 
large puncta described by Donkin being simply the ends standing out 
distinctly on an elevated ridge. 
Arran Islands; Stomachs of Ascidians, Roun’stone Bay, Co. 
Galway. 
