STAURASTRUM. 123 



19-25 [j. ; breadth, including processes, 19-30 k u. ; breadth 

 of isthmus 5-6 ^ . 



ENGLAND. Skipwith Common, N. Yorks ! 



SCOTLAND.- -Benbecula, Outer Hebrides ! 



IRELAND.- -Lakes, near Recess, Gahvay ! 



Geogr. Distribution. Sweden (var.). Ceylon. Siam 

 (var.). New Zealand. Madagascar. Azores. United 

 States. 



This little species is readily distinguished from St. tet racer um 

 by the relatively larger body of the semicell, and its stouter 

 habit. From St. micron West it is distinguished by its cuneate 

 semicells, and its more slender processes with several series of 

 granules. 



127. Staurastrum micron West. 

 (PL CXLIX, fig. 6.) 



Staurastrum micron West & G. S. West, New and Tut. Kreslnv. Alu\ 1896, 

 p. 159, t. 4, f. 50, 51 ; Alg. S. England, 1897, p. 495 ; Freshu . ( 'hlorophy. 

 Koh Chang, 1901, p. 95 ; Alg. X. Ireland, 1902, p. 57, 



Cells very small, about as long as broad, including the 

 processes, deeply constricted ; semicells inversely semi- 

 circular, apex slightly convex ; upper angles produced 

 to form short, stout, diverging processes, each process 

 with two series of short spines near its base, and dilated 

 at its apex, which is truncate and provided with 3 short 

 spines. Vertical view triangular, sides concave, angles 

 produced to form short dilated processes. 



Zygospore unknown. 



Length, without processes, 8*5-1 1*5 \L ; with processes, 

 12-17'5pi; breadth, without processes, 7-9'ojx; with 

 processes, 12'5-19pt ; breadth of isthmus 3-3'5^. 



ENGLAND.- -Puttenham Common, Surrey (abundant) ! 

 Woodbury Common, Devon ! 



IRELAND.- -Near Glenties, and Lough Gartan, Done- 

 gal ! 



Geogr. Distribution. Sweden (var.). Siam (form). 

 W. Africa (var.). 



This tiny species has very constant characters which render 



