346 Proceedings of the Royal Irish Academy. 



Diat., p. 42, T. yi., fig. 19. Do. Fl. Eur. Alg., sect. 1, p. 21 6 (where it is 

 identified with Pinniilaria latestriata.) Gregory Q. J. M. S., Yol. ii.,, 

 1854, PI. iv., fig. 13. Wm. Sm., B.D., Yol. ii., p. 94. 



Drumoughty Lough, near Kenmare, Co. Kerry. Pond near Glen- 

 chree, Co. Wicklow. Ulster Canal, near Poyntzpass, Co. Armagh. 

 Loughbrickland, Co. Down. Cushenden, Lough Ncagh, Co. Antrim^ 

 Featherbed Mountain, Co. Dublin. 



NavicuJa menapiensis, IT. S. Marine. 



Yalve small ; length -0016; breadth •0005; linear, ends rounded 

 and slightly conical. Costce marginal, distant; intermediate free- 

 space tolerably wide, linear elliptical. (PI. 30, fig. 15.) 



This form is, in some respects, similar to the last, but striaj are 

 longer; otherwise distinguished by its marine habitat. 



Sea-weeds, Bannow, Co. Wexford. Stomachs of Ascidians, Broad-- 

 haven Bay, Co. Galway. 



Navicula tabellaria, (Ehr.) Fresh water. 



Yalve oblong, slightly expanded at the middle and ends. Length 

 about -0050 ; breadth about "0007. Costse strong, convergent in the 

 middle, then parallel and radiate towards the ends ; intermediate free 

 space wide, roundly expanded in the middle. (Plate 30, fig. 12.) 



Kiitz. Bac, p. 98, T. xxviii., figs. 79, 80, where the costas are- 

 described incorrectly as reaching the median line ; also T. xxx., fig.. 

 20, where the costa3 are represented as marginal, whereas they extend 

 much further towards the median line. Grunow, Yerhand. dor K. K.. 

 Zool. Bot. Gesel., Band x., 1860, p. 516. Ealfs, in Pritch., p. 896, 

 PI. xii., fig. 21. Cleve, Om Svenska och Norska Diat., p. 224, 

 Donkin., N. H. Brit. Diat., p. 70, PL xii., fig. 4.— Pinnularia 

 tabellaria, Ehr. Wm. Sm., B. D., Yol. i., p. 58, PL xix., fig. 181. 

 Bab. Sussw. Diat., p. 44, T. vi., fig. 24. Do. FL Eur. Alg., sect, i., 

 P-I211. 



Friarstown, Pipcrstown, Featherbed Mountain, Killakee, Co^ 

 Dublin. Glenchree, Lugnaquilla Mountain. Co. Wicklow. Glencar, 

 Co. Kerry. Lough Corrib, Co. Galway. Lough Mourne deposit, Coo. 

 Antrim. 



Navicida tabellaria, var. acrosphcBria, (De Breb.) Fresh water. 



Like the typical form. The costa3, however, are marginal. 



Navicula acrosphaeria, Kiitz. Bac, p. 97, T. v., fig. 11, where 

 it is alleged that the form is identical with Frustulia acrosphaeria,. 

 De Brebisson, to whom, on this account, I attribute the species.. 

 Ralfs, in Pritch., p. 896. — Navicula tabellaria, Grunow, who observes, 

 that " Wm. Smith's figures and descriptions of Navicula acrosphseria 

 and N. tabellaria differ only in the different size and the somewhat 



