O'Meara — Report on the Irish Biatomacece. 385 



Donkin, N. H. Brit. Diat., p. 1 , PI. i. fig. 6. Grunow, Verliand. der 

 K. K. Zool. Bot. Gesell., Band x., 1860, p. 531. Heiberg, De Danske 

 Diat., p. 81. Cleve, Om Svenska och. JSTorska Diat, p. 226. Scliumann, 

 Die Diat. der Hohen Tatra., p. 69. Lagerstedt, Sotvat. Diat. fran 

 Spetsbergen och Beeren Eiland, p. 27. Schmidt, Atlas der Diat., T. 

 Tii. figs. 31, 32.— N'avicula ovalis, Wm. Sm., B. D., Yol. i., p. 48, 

 PI. xvii., fig. 153fl!. 



Tacumshane, Co. Wexford. Lower Lake, Killarney, Co. Keriy. 

 Glenchree, Powerscoiirt, Co. Wicklow. Lucan, Killakee, Boherna- 

 brena, Co. Dublin. Feighcullen, Royal Canal, near Enfield, Co. Kil- 

 dare. Pond, near the city of Armagh. 



Var. costata, (O'Meara). Presh, or brackish water. 



Yalve strongly resembling the typical species, but strise distinctly 

 costate, and intermediate free space included between the inner mar- 

 gins of the inner striate band lanceolate, but slightly expanded in the 

 middle. 



This variety has been found in localities where marine and fresh 

 water forms are mixed. 



Breaches near J^ewcastle, Co. Wicklow. Lough Gill, Co. Kerry. 



Var. davidsonii, (O'Meara). Presh water. 



Yalve ovate-elliptical. Striae very fine, monilif orm ; space included 

 within the inner margin of the inner striate band linear, roundly 

 expanded in the middle. 



This variety was first brought under my notice by my valued corres- 

 pondent, Eev. George Davidson, of Logie, Coldstone, near Aberdeen, 

 who found it in his neighbourhood. It has since been noticed by me 

 in various localities in Ireland. On first view this form would seem 

 to belong to Navicula eestiva, and when first noticed by me in a fresh 

 water gathering, I considered it was a stray form of the species men- 

 tioned, which had come there by accident ; but siibsequent observation 

 induced me to give up this view, and to consider the form a well" marked 

 variety. It is likely the same as that figured by Schmidt in his Atlas 

 der Diat., T. vii., fig. 33. 



Moist Eock. Portrush, Co. Antrim, Lough Mask, near Tourma- 

 keady, Lough jSTeagh, near Lurgan, Co. Armagh. 



Var. ovalis, (Wm. Smith). Presh water. • 



Yalve linear, oblong, with rounded ends ; strise much finer than in 

 the case of the typical form; length about "0016, breadth about 

 •0005. (Plate 32, fig. 22.) 



Navicula ovalis, Wm. Sm., B. D., Yol. i., p. 48, PI. xvii., fig. 153 a. 

 Under the impression that this form and ISTavicula elliptica were iden- 

 tical, Smith abandoned the specific name of ovalis, and merged the two 



