200 DUBLIN NATUBAL HISTOBT SOCIETY. 



happy opportunity be afforded of tracing the organism through its whole 

 course of life, but, on the part of the observer, the requisite leisure and 

 patient assiduity must not be wanting. 



No doubt it is much easier to describe a new species than to demon- 

 state that two, or perhaps more, familiar forms are but 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 distinguished by marks as decided and striking as those by 

 which species, which are universally acknowledged, are separated, pre- 

 sents 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 were 

 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 gradationai variations. To some, however, it may seem premature 

 to describe them without knowing the sporangial state. It will be re- 

 collected, however, that, of very many of the species, as described in 

 Ralfs' ^'British Desmidiae," the sporangium is not known, nor, when 

 known, can there usually he important distinctions dravni from it. I 

 trust the following may serve as a description of the new forms : — 



TamUy.— DESMIDIACE^. 



Genus. — Staueastrum (Meyen, Breh., Ralfs^ Sfc). 



Staurastrum oxyacantha {sp. nov.). 



Specific characters : Frond rough with minute granules ; segments 

 broa(Uy 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 Eoundwood 

 road; rare. 



General Description: Frond nearly as long as broad; segments 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 con- 

 verging with that of the opposite segment, having the granules thereon 

 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-view tri-radiate, having projecting from each side 

 at equal intervals the parallel pair of spines unaccompanied by others ; 

 processes terminating each angle in this view, straight, elongate ; endo- 

 chrome restricted to the centre, tri-radiate. 



Length of frond, 1-770 of an inch ; breadth, 1-580 to 1-636 ; breadth 

 of constriction, 1-2330. 



