O’Mzara—Report on the Irish Diatomacee. 291 
Genus VI. Dzaroma, De Candolle. 
Frustules united in zig-zag filaments ; strongly costate ; costs per- 
vious. 
Grunow states that the various species of this genus, as well as 
those of Odontidium, possess fine strie interposed between the coste, 
although in the former they are more difficult to be discovered than in 
the latter. The most careful examination of the valves of Diatoma, 
on my part, has, as yet, failed to bring them out. 
Diatoma vulgare, (Bory.) Fresh water. 
Valves much arched, so that the coste present a deep margin on 
the front view; on side view the outline is elliptical, sometimes nar- 
rowed towards the ends ; cost strong and close. 
Kiitz. Bac., p. 47, T. xvii., fig. 15, 1-4. Rab. Siissw. Diat., 
Deon Lie oo. NLM. om, .b. D., ;Vols ly, p. 39,-PlexL, fie. 309: 
Ralte im sPriteh.. p.778, liv. fe. 13, Pl.-i:,fig. 168. ‘Grunow; 
Verhand der K. K. Zool. Bot. Gesel., Band xii., 1862, p. 363. Hei- 
berg, De Danske Diat., p. 57. Cleve, Om Svenska och Norska Diat., 
p- 219. Castracane, Catalogo di Diat. raccolte nell Val Intrasca, 
p- 1d. 
River Dodder, Grand Canal at Portobello, Co. Dublin. Well, 
Strokestown, Co. Roscommon. Stream in Glebe, Delgany, Co. Wick- 
low. River Moy, Foxford, Co. Mayo. Stream, Killeshin, Queen’s 
County. River Lee, Co. Cork. 
Diatoma grande, (Wm. 8m.) Fresh water. 
Frustules on front view slightly inflexed; on side view linear, 
shghtly constricted towards the capitate ends; costz fine, close. (PI. 
98, fig. 1.) 
Wouepm.ob. D.. Vola. p39, Pl xil., fe..310. Ralis, m Prtch,, 
p. 779. Heiberg, De Danske Diat., p. 57. Castracane, Catalogo di 
Diat. raccolte nell Val Intrasca, p. 15.—Diatoma vulgare var. grande. 
Grunow, Verhand der K.K. Zool. Bot. Gesel., xii., Band 1862, p. 
364.—Diatoma Ehrenbergiu forma grandis, Rab. Fl. Eur., sect. 1, 
p. 122. Grunow stands alone in subordinating this form to Diatoma 
vulgare, from which it stands distinguished by numerous characters: 
so distinct is it from that species in the outline of the valve, both in 
front and side view, that it seems deserving of occupying the place of 
a separate species. 
River at Belleek, Co. Fermanagh. Tacumshane, River Slaney, 
near Killurin, Co. Wexford. River Shannon, near Athlone, Co. Ros- 
common. Lough Corrib, Co. Mayo. Lough Derg, Co. Galway. 
Lough Neagh, Co. Armagh. Iillikee, River Liffey, Co. Dublin. 
