O’Mrara—Report on the Irish Diatomacee. 249 
Bac., p. 52, T. ui., fig. 3. Wm.Sm., B.D., Vol. u1., p.55. Pl. xlix., 
fig. 329, Ralfs, in Pritch., p. 816, Pl. v., fi. 64 and Pl, x1, fig. 14. 
There is considerable difference of opinion as to the founder of this 
species; Smith assigns it to Kiitzing, Ralfs to Dillwyn and Agardh. 
On this subject Heiberg says, ‘‘As above mentioned, O. F. Muller 
was probably the first to discover this species, and describe it under 
the name of Conferva moniliformis, or strand-necklace, but that can- 
not be ascertained with certainty. The present specific name is 
attributable to Dillwyn, who in 1809 described a Conferva nummu- 
loides, which Lyngbye cites as a synonym under his Fragillaria num- 
muloides. But as meanwhile there do not appear to be any original 
specimens of Dillwyn’s species, and his figures can only be approxi- 
mately identified, while the numerous specimens of Lyngbye which 
still exist are all attributable to our species, it seems most proper to 
name Lyngbye as the author.”” De Danske Diat., p. 29. 
Brackish ditch near Wexford, Malahide, Dollymount, WNorth- 
wall, Co. Dublin. Salt ditch near Wicklow, and many other places 
too numerous to mention. 
Lysigonium Westii, (Wm. Sm.) Marine. 
Frustules somewhat conical, furnished with two keels, one at the 
suture, another near the end, considerably thicker than the similar 
structure in Lys. nummuloides, and not projecting upwards to the 
same extent. 
Melosira Westi, Wm. Sm., B. D., Vol. i1., p. 59, Pl. lii., fig. 333. 
Ralfs, in Pritch., p. 817. Rab. Fl. Eur., p. 38. 
Dollymount, Oyster beds, Howth, Co. Dublin. Near Wicklow. 
Stomachs of Ascidians, Roundstone Bay, Co. Galway. 
Lysigonium Wrightir, (O’Meara.) Marine. 
Frustules rounded at the ends, narrow, surrounded by a broad 
keel, which curving slightly outwards and upwards, then bending in- 
wards and downwards to the surface of the valve, forms round it a 
crown-like rim. In the front view two nodules are observable in the 
central portion of the valve ; the frustule is perfectly hyaline, without 
sculpture of any kind. = 
O'Meara, Q. J. M.S., Vol. ix., Pl. xii., fig. 3. r 
Arran Islands, Co. Galway. 
Genus III. Poposrra, Ehr. 
Filaments attached by a distinct stipes, and generally short, con- 
sisting of a few frustules. 
Heiberg regards the character on which this genus is founded as 
