176 BRITISH DESMIDIACE^}. 



or subfusiform, lateral angles gradually produced into 

 short processes with bifid spreading apices ; with two 

 accessory processes on the faces of the semicell between 

 each two consecutive angular processes and in the same 

 horizontal plane with them, and with two other pro- 

 cesses projecting from the apical margin of each face 

 immediately above the accessory processes of the lower 

 whorl ; processes smooth, or the angular ones sometimes 

 with a circle of minute denticulations. Vertical view 

 triangular, angles very slightly produced ; sides 

 gently concave, each with 2 bifid processes projecting 

 from its margin, and with 2 others just within the margin 

 on the apex. 



Zygospore unknown. 



Length 42-46 pi ; breadth, including processes, 46- 

 58 JJL ; breadth of isthmus 11-1 5 (x. 



ENGLAND.- -Bowness, Westmoreland ! 



IRELAND.- -Dublin and Wicklow (Arch.). 



Geogr. Distribution. Germany. Galicia in Austria. 

 Norway. Sweden. Bornholm. Finland. Poland. Spitz- 

 bergen (form). India. Burma. Australia. United States. 

 Colombia. 



St. senarium is closely allied to St. furcatum Ehr., from which 

 it differs in the possession of 15 processes, instead of 9. The 

 processes are arranged one at each angle, with 6 others in the 

 same plane as these 3 angular ones, and a dorsal series of 6 on 

 the apex. The presence of denticulations on the angular pro- 

 cesses is of little importance, since they are sometimes present 

 in one semicell of an individual and absent from the other. 



162. Staurastrum gemelliparum Nordst. 

 (PL CLVI, fig. 5.) 



Staurastrum gemelliparum Nordst. Desm. Brasil, 1869, p. 230, t. 4, f. 54; 

 Wille, Sydamerik. Alg.-fl. 1884, p. 21 ; De Toni, Syll. Alg. 1889, p. 1175 ; 

 West & G. 8. West, Alg. Ceylon, 1902, p. 179, t. 21, f. 25 ; Borge, Sao 

 Paulo Alg. 1918, p. 54, t. 4, f. 25. 



Cells small, about as long as broad, or a little longer, 

 deeply constricted, sinus open and acute ; semicells 

 subelliptical, dorsal margin nearly straight, ventral 



