248 Proceedings of the Royal Irish Academy. 



in Pritch., p. 817, PI. xv., fig. 32. Heiberg, De Danske Diat., p. 27. — 

 •Gallionella varians, Ekr. Inf. T. x., fig. 4. 



Very common in streams and fresh springs. 



Melosira distans, (Kntz.) Fresh, water. 



Frustules short, bnt slightly convex at the ends, distinctly punc- 

 tate. (PI. 26, fig. 3.) 



Kiitz. Bac, p. 54, T. ii., fig. 12. Eab. Die Siissw Diat., p. 13, 

 T. ii., fig. 9. Wm. Sm. B.D., Yol. ii., p. 58, PI. lxi., fig. 385. 

 Ralfs, in Pritch., p. 818. — Gallionella distans, Ehr. Inf., p. 170, 

 T. xxi., fig. 4. 



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 insufiicient to justify their separation." B.D., Yol. ii., 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. 



Killikee, Dundrum, Co. Dublin. Kilcool, Co. "Wicklow. Pond 

 near Armagh. 



Genus II. LTsiGOjfnjM:, Link. 



Prustules globose or cylindrical, valves furnished with an elevated 

 Tieel 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 Westii Wm. Sm., which does not occur in our country, 

 may also be referred. The name Lysigonium was in the first instance 

 applied by Link, to 0. 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 niDmmdoides, (Lyngbye, Kiitz.) Marine. 

 Ordinary frustules, globose. Keel thin, in front view appearing as 

 lines projecting like horns. (PI. 26, fig. 4.) 



Heiberg, De Danske Diat., p. 29. — Melosira nummuloides, Kiitz. 



