342 Proceedings of the Royal Irish Academy, 



among the ISTobilcs, to be ouly a variety of Xavicula yiridis. Speaking 

 of this former, he says, "it appears to me to be only a variety of Nav. 

 viridis, tolerably niimeroiis figures (especially from specimens out of 

 the Kieselguss of Franzensbad), "svhich lie before me, present such 

 manifold transitions, as •well in respect to the appearance of the stria- 

 tion as to the outline of the form, that in most cases it is difficult to 

 decide whether the specimen should be referred to one or the other." 

 Yerhand. der K. K. Zool. Bot. Gesel., Band 5., 1860, p. 515. 



The correctness of this remark is obvious to all careful observers, 

 but still the species seem to be distinct. The foUoTving characters 

 seem to distinguish iSFavicnla viridis fi'om IST. major; the costee arc 

 finer and less radiate ; the median free space is narrower and less ex- 

 panded around the central nodule, and the normal outline is linear 

 ellijotical. 



• Ktitz. Bac, p. 97, T. iv., fig. 18. llalfs, in Pritch., p. 907, PL ix., 

 figs. 135, 136. Grrunow, Yerhand. der K. K. Zool. Bot. Gesel., Band 

 X., 1860, p. 518. Heiberg, De Danske Diat., p. 80. Cleve, Om 

 Svenska och Norska Diat., p. 223. — Pinnularia viridis, Wm. Sm., 

 B.D., Yol. i., p. 54, PI. xviii., fig. 163. Eab. Siissw. Diat., p. 42, T. 

 vi., fig. 4. 



Featherbed Mountain, Friarstown, Co. Dublin. Piver Erne, near 

 Crossdoney, Derrylane Lough, Co. Cavan. Ditch near Cushendun, 

 Co. Antrim, Drumoughty Lough, near Kenmare, Lower Lake, Kil- 

 larney. River near Grlencar, Co. Kerry. Greenane Carrickmacreilly 

 Hill, Lugnaquilla, Co. AYicklow. Lough Corrib, Co. Galway. Lough 

 Mourne deposit, Sub-peat deposit, Dromore, Co. Down. 



Kavicxda alpina, ("Wm. Sm.) Fresh water. 



Length of valves about "0060, breadth about '0018 ; broadly ellip- 

 tical, with rounded ends ; intermediate free space wide, but slightly 

 expanded around the central nodule ; costfe broad, convergent in the 

 middle, and radiate towards the ends. (PI. 30, fig. 4.) 



Grunow, Yerhand. der K. K. Zool. Bot. Gesel., Band x., 1860, p. 

 522. — Pinnularia alpina, Wm. Sm., B. D., Yol. i., p. bh, PL xviii., fig. 

 168. Eab. Fl. Eur. Alg., sect. 1, p. 213. 



On the slopes of Slieve Donard, Co. Down. Killakee, Featherbed 

 Mountain, Co. Dublin. 



Navicida paclxyptera, (Ehr.) Fresh water. 



Frustules regularly quadrangiilar on front view ; length of valve 

 about -0034, breadth about -0013; slightly inflated in the middle, 

 rounded at the ends ; intermediate free space but slightly expanded in 

 the middle; costse broad, slightly converging in the middle, and nearly 

 parallel for the remainder. (Plate 30, fig. 5.) 



Kiitz. Bac, p. 98, T. xxviii.. fig. 58. Ralfs, in Pritch., p. 896, 

 who considers the species distinct from Pinnularia lata, Wm. Smith, 



