254 Proceedings of the Royal Irish Academy. 



deviates so much from the normal appearance of the species, that one 

 may almost take it for certain that it represents a very different form, 

 for a diiference of so much importance could scarcely have arisen from 

 inadvertence." — De Danske Diat., p. 31. In Thwaites' original 

 description of Aulocoseira crenulata, Kiitz. =Melosira orichalcea, Ralfs 

 (and Orthosira orichalcea, Wm. Sm.), both the generic definition and 

 the figure are inapplicable to the present species as figured by Smith. 

 " Atilacoseira cellulis cylindricis, hisidcatis, extremitatibus plus minusvo 

 rotundatis, in filamenta concatenatis." Ann. of Nat. Hist. March, 

 1848, p. 7, most correctly describes Orthosira Eoeseana, Rab. = 0. 

 spinosa ("Wm. Sm.). The frustules, as described ib. PI. xi., B., figs. 

 1, 2, and 3, are greatly more like that form than any other species, 

 and the side \ie-^, as represented in the sporangial frustule, is pre- 

 cisely as the side view of that species is described by Smith, B. D., 

 Vol. ii., p. 62, PI. Ixi., fig. 386. I am therefore disposed to think 

 that it was not Orthosira orichalcea, but Orthosira Eoeseana, which 

 Thwaites observed in the process of forming sporangia, or, as Pfitzer 

 designates them, Auxosporcs. 



Smith's Irish localities are — Well at Seven Chiu'ches ; Clonmac- 

 noise ; Moanarone, County Cork ; Lough Moume deposit ; to which I 

 have to add the following : — Eiver Erne, Crossdoney, County Cavan ; 

 Lough Islandi^eavy, County Down ; Lough I^eagh, near the town of 

 Lurgan, County Armagh ; Killakee and Glenchrec, County Dublin. 



Orthosira punctata, (Wm. Sm.) Presh water. 



This species is distinguished fi'om the preceding chiefly by the fact 

 that in this the puncta are very much larger, and more regularly 

 arranged ; they are parallel to the suture, and so regularly placed that 

 they sometimes appear to run spirally. Heiberg remarks that " Smith's 

 species is easily recognised by the obvious rows of puncta crossing one 

 another, which run in oblique spii'als from the suture up to and over 

 the side view." — De Danske Diat. p. 31. These last words seem to 

 imply that the side view is punctate like the front view ; if so, then 

 the species must be regarded as certainly distinct from the preceding. 

 Smith does not figure the side view, and, in consequence of the length 

 of the frustule, it is difiicult to turn it over so as to get it under 

 observation. In one case only could I get a view of it, and then only 

 obliquely ; in this aspect it appeared strongly punctate. The circle of 

 spines at the suture is absent in this species as in the last. 



Ealfs, in Pritchard, p. 820, makes this species synonymous with 

 Melosira granulata = Gallionella granulata, Elir. and Eabenhorst, PI. 

 Eur., p. 43, adopts the same course ; but so much uncertainty charac- 

 terises Ehrenberg's figures of that species, I prefer, with Heiberg, to 

 adopt the precise figure of Smith, and attribute the species to him. 



Ulster Canal, near Poyntzpass. Lough Neagh, near Lurgan, County 

 Armagh, 



