O’Mrara—Report on the Irish Diatomacee. 287 
Odontidium hyemale, (Lyngb.) Fresh water. 
Frustules in long filaments; valve on side view narrow, elliptical ; 
coste strong, about ten in number, with distinct linear strie between 
the coste ; ends of cost on front view forming a narrow margin. 
Kiitz. Bac., p. 44, T. xviil., fig. 4. Rab. Siissw. Diat., p. 34, T. i, 
fed. Wane.om,,: Bs Ds Vow... p: Lo, Pl. xxxiv., fig: 2892) Ralfs; 
in Pritch., p. 775, Pl. xiu., fig. 25. Grunow, Verhand der K. K. Zool. 
Bot. Gesel., Band xii., 1862, p. 356.—Diatoma hyemale, Heiberg, De 
Danske Diat., p. 58. Cleve, Om Svenska och Norska Diat., p. 219. 
—Fragilaria hyemalis, Lyngb., Tent. Hydr. Dan., p. 63. 
Wet rock, Black Castle, Co. Wicklow. Streamlet near Belfast, 
Co. Antrim. 
Odontidium mesodon, (Ehr.) Fresh water. 
Frustules united in long filaments, shorter, wider, and broader 
than in the preceding species; on side view broadly elliptical, with 
three to five strongly developed coste, which, in consequence of the 
greater convexity of the valve, appear longer on the front than in the 
foregoing species; fine stria may be discovered between the costz 
without much difficulty. (Pl. 27, fig. 18.) 
Heiberg attributes the species to Lyngbye, Smith to Kiitzing; but 
as Kiitzing himself identifies it with Fragilaria mesodon of Ehr, and 
the Fragilaria hyemalis of Lyngbye is regarded by the same writer as 
identical with both Odontidium hyemale and O. mesodon, the species 
may properly be referred to Ehrenberg. 
Kiitz. Bac., p. 44, T. xvii., fig.1. Rab. Stissw. Diat., p. 34, T.i7., 
fie, 2 Wm. Sms, BLD: Vol. u., p. 16, Pl. xxxiv., fig: 288. -Ralis, in 
Pritch., p. 75.—Odontidium hyemale var. mesodon, Grunow, Verhand 
der K. K. Zool. Bot. Gesel., Band xii., 1862, p. 357.—Fragilaria 
mesodon, Ehr. Mic., T. 11., fig. 9—Diatoma hyemale, Heib., De Danske 
Diat., p. 58. Cleve, Om Svenska och Norska Diat., p. 219. Both 
these last named authors regard this and the preceding species merely 
as varieties. 
Friarstown, Piperstown, Co. Dublin. Glenchree, Powerscourt, 
Co. Wicklow. Well at Farraghy, River Dour, Co. Cork. 
Odontidium anomalum, (Wm. 8m.) Fresh water. 
Filaments short; frustules on front view usually exhibiting in- 
ternal cells, hkely the result of imperfect self-division; on side view 
narrow, linear, slightly constricted at the ends. Cost strong, about 
eight or ten in number. 
Wanwom., Ba), Vol, i. p: 16, Supp.cel. Ixi., fig. 376. Ralts, in 
Pritch., p. 776. Grunow, Verhand der K. K. Zool. Bot. Gesel., Band 
XAij, 1862, p. 357, T. iv., fig. 4. Rab. Fl. Eur., sect. 1, p. 116. 
Ditch near Newcastle, Co. Wicklow. This form is usually found 
in Alpine districts. 
