ARCHER AND DIXON, ON DESMIDIACE/E. 77 



different states or phases of one and the same organism. 

 Nevertheless, when a form undescribed and quite distinct 

 from any of its nearest allies in the same genus, and distin- 

 guished by marks as decided and striking as those by which 

 species, which are universally acknowledged, are separated, 

 presents itself occasionally, perhaps abundantly, and which 

 may as likely be met with by other observers, it seems to me 

 right, nay essential, that it should be distinguished by a 

 name, and its diagnostic characteristics carefully recorded. 



I offer the foregoing remarks, which it may be proper to 

 state Avere written considerably before the Hymenophyllum 

 discussion arose, as apologetic for my venturing to bring forward 

 the following description of two species of Staurastrum ; and 

 yet, perhaps, they are not strictly applicable, for these new 

 forms appear to me abundantly distinct from every other 

 species, and in no way to be mistaken for mere intermediate 

 or gradational variations. To some, however, it may seem 

 premature to describe them without knowing the sporangial 

 state. It will be recollected, however, that, of very many of 

 the species, as described in Ralfs' ' British Desmidiese,' the 

 sporangium is not known, nor, when known, can there usually 

 be important distinctions drawn from it. I trust the follow- 

 ing may serve as a description of the new forms : 



Family Desmidiace^:. 



Genus Staurastrum, Meyen, Brtb., Ralfs, &c. 



Staurastrum oxyacantha (sp. nov.) 



Specific characters : Frond rough with minute granules ; 

 segments broadly fusiform, with incurved processes ; end view 

 tri-radiate, each side having, disposed at equal distances, a 

 pair of depressed, slender, subulate, acute spines. 



Locality : Pools near " Sugar-loaf" Mountain, on the 

 Roundwood road ; rare. 



General description : Frond nearly as long as broad ; seg- 

 ments rough, with minute granules, broadly fusiform, inner 

 margin somewhat more turgid than the outer, and forming 

 at constriction a broadly triangular notch, tapering at each 

 side into a colourless process incurved or converging with 

 that of the opposite segment, having the granules theron 

 arranged in transverse lines, and cleft at the extremity into 

 three or four minute subulate spines ; frond furnished at ends 

 upon each side with a pair of slender subulate, acute, 

 depressed spines, which are apparent in the front view. End 



