402 Proceedings of the Royal Irish Academy. 



ments on either side of the median one Tvider than they appear in my 

 specimens. Schmidt, Atlas der Diat., T. xii., fig. 51. In outline, 

 this figure exactly represents the present species ; the striation, how- 

 ever, seems different. 



Arran Islands ; Stomachs of Ascidians, BroadhaTen Bay, Co. Gal- 



Namcida didyma, (Ehr.) Marine. 



Yalves slightly constricted ; median compartment wide, inflexed 

 at the ends, greatly constricted in the middle ; compartments on either 

 side Teiy narrow, exhibiting a row of moniliform dots on the inner 

 margin ; marginal striate hand broad ; striae radiate throughout, closely 

 moniliform; length about •0030, breadth "0011 ; breadth at the con- 

 striction -0010. "(Plate 33, fig. 29.) 



Kiitz. Bac, p. 100, T. iv., fig. 7, T. xxviii., fig. 75. In the former 

 figure, the compartments at either side of the median one are repre- 

 sented as much wider than in my specimens ; in the latter figure the 

 strise are rejiresented as running up to the outer margin of the median 

 compartment, the compartments at either side being thus wholly 

 obliterated. Kiitzing attributes the species to Ehi'enberg. "Wm. Sm., 

 B. D., Vol. i., p. 53, PI. xyii., fig. 54. Ealfs, in Pritch., p. 893, 

 PL xii., fig. 15. Ealfs' figure of the species, PL vii., fig. 61, is more 

 lite jSTaTieula interrupta than J^avicula didyma. GrrunoAv, Yei'hand. 

 der K. K. Zool. Bot. Gesell., Band x., 1860, p. 530. Cleve, Om Svenska 

 och iSforska Diat., p. 225. Donkin, IST. H. Brit. Diat., p. 51, PL yii,, 

 fig. 8. 



The form described by Ptabenhorst as Pinnularia didpna, Siissw. 

 Diat., p. 46, T. vL, fig. 26, is probably the same as the present spe- 

 cies, bxit if so, its occurrence in fresh water must have been casual. 



Bannow, Eiver Slaney, at Killurin, Tacumshane, Co. YJ^exford. 

 Malahide, Portmarnock, Piles of wooden bridge, Dollymount Strand, 

 Co. Dublin. Lough Poyle, Co. Derry. Salt-marsh, near town of 

 "Wicklow. Kilkee, Co. Clare. Arran Islands ; Stomachs of Ascidians, 

 Eoundstone Bay ; Stomachs of Ascidians, Broadhaven Bay, sea- 

 weeds near Westport, Co. Galway. Stomachs of Ascidians, Belfast 

 Lough, Co. Antrim. 



Navicida splendida, (Gregory). Marine. 



Yalve large, deeply constricted ; median compartment wide, 

 greatly inflexed at the ends, greatly constricted in the middle ; com- 

 partments at either side narrow, having the inner edge milled ; mar- 

 ginal band of strife narrow in the middle, widening in a gTaceful curve 

 towards the middle of the lobe, then narrowing towards the somewhat 

 lanceolate ends ; striee convergent in the middle, radiate towards the 



