O’Mrara—Report on the Irish Diatomacee. 253 
to what he had noticed in Meridion circulare and M. constrictum, 
Himantidium Soleirolii, Odontidium anomalum, and Achnanthes sub- 
sessilis. I add the interesting description given by Pfitzer of an ano- 
malous procedure noticed by Fr. Schmitz in the development of 
Orthosira spinosa, as likely to throw some light on the subject. ‘“‘ A 
separation of the firstling-cell followed, not immediately, but a devia- 
tion occurred analogous to what has been described in the case of 
Navicula ambigua. First one girdleband was developed, the length 
of which was about that of the radius of the cell. This girdleband, 
according to Fr. Schmitz, was attached only to one valve; that which 
ought to have been connected with the other valve, if it existed at 
all, was only rudimentary. Then the plasm moved about only in that 
half of the cell to which the girdleband adhered, and secreted a new 
valve, which, as might be expected, was parallel to the original one 
destitute of the girdleband. In the cell so originating, division then 
took place in the normal manner, only that the one end-cell of the fila- 
ment in course of formation, instead of two valves possessed three. 
Inasmuch as a small portion of the plasm remained behind, between 
the two parallel valves, and then died off, Fr. Schmitz was inclined 
to think the procedure was an abortive attempt at self-division, one 
portion of the plasm being too small to develop itself into a daughter- 
cell.”” Ueber Bau und Entwicklung der Bac., p. 135. 
Ditch on bank of Royal Canal, near Kilcock, Co. Kildare. It is 
likely this species is more common than it appears from the few lo- 
calities assigned to it, as in its normal condition it may be easily con- 
founded with Melosira varians. 
Orthosira orichalcea, (Wm. Sm.) Freshwater. 
The circle of puncta that in most of the species of this genus runs 
parallel with the suture is not observable in this. Spines on junction 
surfaces distinct ; valve not striated on the side view, except on the 
margin, where the points of the spines appear as small puncta. Frus- 
tules striated,on front view. Strie fine, punctate, parallel. (Pl. 26, 
fig. 8.) 
Ralfs and Rabenhorst have referred this species to Mertens on the 
authority of Kiitzing, who has figured and described a form under this 
specific designation. The figure of Melosira orichalcea, Bact., T. ii., 
fig. 14, is by no means definite, and one feature in the description 
suggests the impression that he had quite a different species in view. 
“* Sub epidermide silicea leviter bis contractis,” Bac. p. 54, may pos- 
sibly refer to Orthosira spinosa, but not to Orthosira orichalcea, as 
figured by Smith, to whom Heiberg considers the species should be 
attributed, as he was the first to give a description and figure by 
which it could be satisfactorily identified. Heiberg makes the follow- 
ing shrewd observation under Orthosira orichalcea :—‘‘ The figure by 
which Smith describes the process of conjugation in the species under 
consideration, and which he copied from Thwaites’ original delineation, 
2L2 
