STAURASTRUM. 157 



2 others just within the margin ; angles produced to 

 form short processes. 



Zygospore unknown. 



Length. 60-77 ^ ; breadth, including processes, 42- 

 48 [JL ; breadth at base of semicell 14-15 (j. ; breadth of 

 isthmus 9 \JL . 



SCOTLAND.- -oole we, Ross; Glen Coe. Argyle (Roy 

 & Biss.). Ehiconich, Sutherland ! 



IRELAND. Kvlemore. Galwav, and Glengariff, Cork 



/ ^ ~ ~ 



(Arch.). 



Geogr. Distribution. --Sow-ay. Sweden. United States. 



This characteristic species cannot be confused with any other, 

 the form and proportions of its cells being most striking. It is 

 extremely localized in its distribution, and is only known from 

 one or two localities in the western areas of the British Isles. 



150. Staurastrum barbaricum W. & G. S. West. 



(PL CLI, fig. 6.) 



^/<tur(ts/ru)/i l><irli<iri<-/int West & (> . S. West, Alg. N. Ireland, 1902, p. 53, 

 t. 1, f. 23. 



Cells small. Ij times broader than long, including the 

 processes, deeply constricted, sinus open ; semicells 

 elliptic-obsemicircular, lower margins biundulate, apex 

 convex and undulate, angles produced to form very 

 short slightly diverging processes, with 3 tiny spines at 

 their apex, and 2 series of denticulations ; vertical view 

 triangular, sides concave, angles deeply cleft, each 

 forming two short slightly diverging processes. 



Zygospore unknown. 



Length 30 \L ; breadth, including the processes, 38- 

 41 [i ; breadth of isthmus 8 \L. 



IRELAND. Bog near Lough Xeagh, Londonderry ! 



This remarkable Staurastrum stands alone in the possession 

 of two denticulate processes at each angle, arranged in a hori- 

 zontal plane. These processes, which are terminated by 3 small 

 teeth, each possess 2 rings of denticulations. and are disposed in 

 precisely the same manner as the smooth processes of St. Iceve 

 Ealfs, and St. fissum Turn. 



