248 Proceedings of the Royal Irish Academy. 
- in Pritch., p. 817, Pl. xv., fig. 32. Heiberg, De Danske Diat., p. 27.— 
Gallionella varians, Ehr. Inf. T. x., fig. 4. 
Very common in streams and fresh springs, 
Melosira distans, (Kutz.) Fresh water. 
Frustules short, but slightly convex at the ends, distinctly punc- 
tase. CE]. 26,\fig,-3.) 
Kiitz. Bae:, p. 54, T. u., fig. 12. Rab. Die Siissw Diat.; p. 13, 
2 ., fig: 9: Wm, Sm. BD, Vol. a.) p. 58, Piano one: 
Ralfs, in Pritch., p. 818.—Gallionella distans, Ehr. Inf., p. 170, 
Dx, lee. 
Smith describes this species as ‘‘ obscurely cellulate,’”’ and distin- 
guishes it on this ground from his Melosira nivalis, which he charac- 
terises as ‘‘ distinctly cellulate,’’ but remarks that ‘this character is 
probably insufficient to justify their separation.”” B.D., Vol.i1., p. 58. 
The forms occurring in the Bilin Polirschiefer, one of the localities 
assigned by Kiitzing to Melosira distans, are most distinctly punctate; 
I am therefore disposed to consider that Smith’s species, Melosira 
nivalis, cannot be sustained. 
JKollikee, Dundrum, Co. Dublin. Kiulcool, Co. Wicklow. Pond 
near Armagh. 
Genus II. lJiysrconrom, Link. 
Frustules globose or cylindrical, valves furnished with an elevated , 
keel which runs parallel with the sutures; in other particulars as in 
Melosira. 
I have adopted this genus in deference to the authority of Heiberg, 
who, referring to Lysigonium nummuloides, remarks, ‘‘ This species, 
which by all the more recent authors has been assigned to the genus 
Melosira, in my judgment ought to constitute a type of a new genus to 
which Melosira Westi1 Wm. Sm., which does not occur in our country, 
may also be referred. The name Lysigonium was in the first instance 
appled by Link. to O. F. Muller’s Conferva moniliformis, with which 
in all probability this species is identical; and for this reason it seems 
most convenient to re-establish the genus to receive it.’? De Danske 
Diat., p. 29. Heiberg further remarks, ‘‘ that the known species form 
shorter or longer filaments, attached or free ;”’ but I have never seen 
any of the filaments attached. 
Lysigonium nummuloides, (yngbye, Kiitz.) Marine. 
Ordinary frustules, globose. Keel thin, in front view appearing as 
lines projecting like horns. (Pl. 26, fig. 4.) 
Heiberg, De Danske Diat., p. 29.—Melosira nummuloides, Kiitz. 
