320 freshwatp:t? Alg^. of lismore district^ 



Closterium gracile Breb. 



Long. 1 66, lat. 6, ap. 2 ji. 



Lismore (254, 260); Wyrallah. 



The breadth of our specimens of 67. gracile is nearly always 

 6 /x, occasionally 7 [x. It is evident from Brebisson's note (Liste, 

 p. 155) that the generally accepted type of this species is not 

 what its author had in view. He says " peu attenue aux 

 sommets qui sont legereraent courbes et obtus." The blunt- 

 ended form, therefore, is, strictly speaking, Brebisson's type, and 

 this accounts for the curious shape of the apices in his figures. 

 This point, however, is not mentioned in the Latin description. 

 Var. ELONGATUM W. & G. 8. West. 



Long. 300, lat.7, ap.2 /x. 



Lismore (223). 



Cf. Monog., i., p. 168; the authors give lat. 3-4//, but, in this 

 country, its breadth ranges from 5 to 8 /x. 



Var. BicuRVATUM (Delp.) mihi. 



Forma CI. gracilifi sjepissime bi-undulata, apicibus obtusis 

 truncatis. 



Long. 265-400, lat. 6, ap.3/x. 



Lismore (260). Cum f. typica. 



I first obtained this form many years ago in profusion, from 

 weeds out of a tank in the Botanic Gardens. There is no doubt 

 ^of its being CI. bicurvatum Delp., Desm. Subalp., ii., p. 209, T.18, 

 f.37-39. The hollow back, which makes it bi-undulate, and the 

 blunt ends sufficiently characterise it. It is also certainly a 

 form of CI. gracile, cf. Borge, Feuerland u. Isla Desolacion, p. 30, 

 fig.6. CI. toxon West, in Monog. i., p.l60, P1.20, f.l3, 14, is 

 really Si, forma crassior of this variation. 



Var. SUBSTRIGOSUM (Rac.) mihi. (PI. xli., f.8.) 



Forma CI. gracilis apicibus subrostratis, extremis acutis. 



Long. 114-250, lat. 5-6, rarius 8/x, ap. lJ-2/x. 



Lismore (260). 



Syn., CI. macilentum /3 stibstriyosura Rac, Desm. Ciast., p. 9, 

 T.l, f.38; CI. suhstrigosum W. k G. 8. West, Alg. fr. Burmah, 

 p. 19 2, PI. xiii., f.l9. In this form, the sides do not converge 



