322 FRESHWATER ALGM OF LISMORE DISTRICT, 



common, however, at Lismore, especially in shallow meres and 

 pools on grassland, and is not infrequent round Sydney. Aus- 

 tralian forms differ from the European in being less regularly 

 arcuate, much straighter in the back, and suddenly bent in, about 

 one-third of the distance from the ends. Also particularly in 

 the tip, which is only the very slightest bit recurved (not at all 

 as in Monog. i., PI. 21, f.1-3). The membrane is nearly always 

 pale yellow or pale buff, and not striate. 



Forma brevior West. 



Long. 162-345, lat. 18, ap. 4/x. Membrana dilute luteola. 



Lismore (223, 236, 254). 



Cf. CI. prcelongum var. strigosum (Breb.)('?), these Proceedings, 

 1908, p.605, PL xi., f.3; which gives a good idea of Australian 

 forms of CI. prcdonguTn, but the extreme tip should be very 

 slightly recurved. I doubt very much if the form figured. I.e., 

 is identical with CI. strigosum Breb.; it is a specimen of CI. 

 prcelongum f. brevior West, in which the tips are quite straight, 

 not recurved at all. The dimensions may be taken as including 

 f. brevior, as my description says "apicibus .... nonnunquam 

 levissime reflexis.'" There is no real difference either between 

 f. brevior and CI. tumidum Johnson; they are only degrees in 

 reduction; the recorded length of CI. tumidum overlaps that of 

 f. brevior, and the length of the latter runs right up to the type. 

 They all three have the same range of breadth; CI. prcelongum 

 lat. 14-24, f. brevior 16-24, CI. tumidum 18-24 /x are my records. 



Closterium tumidum Johnson. 



Long. 150-180, lat. 23-24, ap. 5-6 /x. Membrana dilute luteola. 



Lismore (236). Cum priori. 



CI. tumidum Johnson (syn., CI. cornu in Wille, Fersk. Nov. 

 Semlja, T. xiv., f.80, 81) is biologically a form of CI. jjrcelongum 

 very much reduced by repeated self-division. I find it always in 

 company with forms of that species. The membrane and apices 

 also are of the same character in both. Repeated division im- 

 mensely reduces the length of the cell without alteration of the 

 breadth. 



