160 MR. W. WEST ON THE .FRESHWATER 



examples were Been, and none of them showed any signs of 

 the familiar characteristic appearance appertaining to stages of 

 division. 



I also think that Cos murium excavatum, Nord., var. ellipticum, 

 AVille (Ferskv. Alg. fr. Nov. Semi. p. 47, tab. 13. fig. 46), is a 

 variety of C. isthmiam, as his measurements (long. 29 p ; lat. 23 p ; 

 crass. 20 /i; lat. isthm. 11 fx) come nearer to a shortened form 

 of it, moreover its granules and excavation are much nearer to 

 those of the latter; I propose to call it var. Willei, nob. Prof. 

 Lagerheim (Bidrag til Amerikas Desmidie-Flora) enumerates 

 C. excavatum, Nord., and gives the following measurements; 

 Long. 44 fx; lat. 24 ju; lat. isthm. 12 /*: judging from these 

 dimensions, the plant he describes seems to belong to G. isthmium 

 rather than to C. excavatum. The var. trigonum, Lagerh. (/. c), 

 of the latter species is so widely different in comparative length 

 and breadth (long. 20 /x ; lat. 18 /x ; crass. 18 /x ; lat. isthm. 13 /x) 

 as well as in its trigonal vertical aspect, that it is probably a 

 distinct species, and may possibly belong to the genus Stau- 

 rastrum. 



Ifs. {Brit. Desm. p. 107, 



) 



Long. 21-28 fx ; lat. 11-13 fx ; lat. isthm. 4-8 ^. 



I. Near Oughterard ; Creggan Lough ; Lakes, Clif den to 

 Eoundstone ; Lakes east of Lough Bofin ; Ballynahinch ; Derry- 

 clare Lough. — II. Cromagloun; Glen Caragh ; Lower Lake of 



Killarney ; Adrigole ; Cloonee Lough. 



Forma semicellulis subrotundatis (levissime subangularibus). 



Long. 38-42 fx; lat. 18-20 /x; lat. isthm. 4-5 fx. 

 I. Ballynahinch. 



92. C. contract™, Kirch. {Wolle, Desm. TJ. S. p. 63, 

 tab. 16. fig. 1, tab. 50. fig, 24.) 



I. Ballynahinch; Clifden ; Lough Aunierin.— II. Cromagloun; 



Adri 



Hedivigia, vol. ii. p. 52, tab. 9. 



fig. 8. 



Long. 30 [x : lat. 25 [x ; lat. isthm. 17*5 /*. 

 I. Lakes east of Lough Bofin. 



