292 W. AND G. S. WEST 



tibus; trichomatibus angustissimis, laete eeruginosis, inter cellulas plus minusve 

 constrictis, apicibus rectis non attenuatis nee capitatis; cellulis tarn longis quam 

 latis vel paullo longioribus, contentu homogeneo. 



Crass, trich. 0.8-0.9 M; long. cell. 0.8-1.1 M. 



Hob. Blue Lake, Coast Lake, and Clear Lake ; in great abundance and forming 

 extensive sheets. 



This species was one of the most abundant of the Blue- green Algae which occurred 

 in certain of the frozen lakes. Most of the specimens were obtained by melting the 

 blue- green sheets from the ice, where they must remain frozen sometimes for several 

 years. It is allied to Ph. angustissimum, but forms a thicker stratum, has slightly 

 thicker and more contorted trichomes, and has shorter cells. 



60 Phormidium angustissimum W. & G. S. West 



" Welw. Afric. Freshw. Algae," Journ. Bot. Aug. 1897, p. 72. 



Crass, trich. 0.6-0.7 M ; long. cell. 2-4 /j.. 



Hob. Deep Lake, forming thin papery sheets of considerable extent and about 

 0.1-0.2 mm. in thickness. 



This species was only observed from this one lake, forming extensive sheets 

 similar to those formed by Ph. glaciale, but much thinner. The trichomes are densely 

 intricate and flexuose, but are not so contorted as those of Ph. glaciale, and the cells 

 are much longer than in that species. 



61 Phormidium antarcticum sp. n. (PI. XXV, Figs. 74, 75a-75<?) 



Ph. filis non in strato associatis, sed inter algas varias Myxophycearum libere 

 natantibus, brevibus ; vaginis indistinctis, plerumque diffluentibus ; trichomatibus 

 brevibus vel brevissimis, pallide serugineis, valde et subirregulariter spiraliter contortis, 

 apicibus obtusis et non attenuatis; cellulis diametro trichomatis 1-2-plo longioribus, 

 contentu homogeneo. 



Crass, trich. 0.6 M; long. cell. 0.6-1.2 M. 



Hob. Pony Lake. 



This minute and much- twisted Phormidium was present in quantity in the 

 sediment obtained from under the ice of Pony Lake both in April 1908 and in 

 January 1909. It was not observed in any of the other collections, and occurred 

 mixed with various Green and Blue-green Algse. The trichomes are very short 

 and invariably twisted into some form of spiral, although they exhibit great 

 irregularity. 



It need not be confused with any of the spirally twisted piankton species 

 of Lyngbya. It has no definite sheath, and is smaller and narrower than any of 

 them. Some specimens showed slight indications of a sheath which had become 

 diffluent, otherwise the Alga might be regarded as an irregular species of the genus 

 Arthrospira. 



