THE GREEN ALGAE OF NORTH AMERICA 39 



sis may be kept as a subgenus, following Wille, with this one 

 species. 



22. T. LIMNETICUM Borge, 1900, p. 5, PI. I, fig. 2. Cell 

 tetraedral, angles extending into long arms, each with 2 short 

 spines at tip; cells 65-70 /* diam., arms about 8-10 ft diam. 

 Wis., G. M. Smith. Europe. 



23. T. PUSILLUM (Wallich) G. S. West, 18973, p. 237 ; 

 Micrasterias pusilla Wallich, 1860. p. 281, PI. XIII, fig. 13. 

 Cells flattened, cruciate, arms each with 2 crooked spines at 

 end; cells 25 ft wide, 10 ft thick. Wis., G. M. Smith. India. 



24. T. PLANCTONICUM G. M. Smith, 1916, p. 479, PI. 

 XXVI, figs. 19-20. Cells 4-5-sided, sides generally incurved 

 and equal ; angles of cells prolonged into bifurcate or trifurcate 

 processes ending in 2 or 3 horns; processes broad in top view, 

 narrow in side ; cells without processes 18-24 P diam., with 

 processes 50-70 ft diagonal diam., diam. of processes 9-12 X 

 5-8 /, length 15-25 p.. Wis., G. M. Smith. 



25. T. FLORIDENSE W. & G. S. West, 1898, p. 7. Cells 

 irregularly octaedral, sides slightly convex, angles forked, with 

 a somewhat curved spine on each fork ; cells 34-44 ft without 

 spines, with spines 44-59 /*. Deland, Fla. 



26. T. LOBULATUM (Nag.) Hansgirg, 1888, p. 132; Polye- 

 drium lobulatum Nageli, 1849, p. 84, PI. IV, B, fig. 3 ; Reinsch, 

 1867, p. 78, PI. II, fig. II. Cells irregularly and indistinctly 

 tetraedral, sometimes flattened, margins from straight to deeply 

 concave ; angles usually 2-parted, each part with 2, rarely 3 

 points, very rarely the angle only emarginate ; width 30-74 ft. 

 Wis., G. M. Smith. Europe. 



Var. POLYFURCATUM G. M. Smith, 1916, p. 480, PI. XXVI, 

 figs. 21-22. Prolongations branching 3-5 times, ultimate divi- 

 sions with 3 spines ; prolongations nearly as long as body of 

 cell; diam. 10-20 ft without processes, 30-40 ft with processes; 

 diagonal diam. 35-50 fi. Wis., G. M. Smith. 



This variety seems transitional between the forms with 

 spinous angles and those with distinctly arm-like prolongations. 



27. T. PROTEIFORME (Turn.) Brunnthaler in Pascher, 1915, 

 p. 152, fig. 177. Polyedrium proteiforme W. B. Turner, 1892, 

 p. 158, PI. XX, fig. 24b. Cells fusiform or triangular, with 

 sinuate sides and prolonged angles, each passing into a spine, 

 not sharply distinct from the cell disk ; fusiform individuals 

 about 65 ft long, 12 ft wide ; triangular 36 fi diam. with spines. 

 Wis., G. M. Smith. India. 



