THE GREEN ALGAE OF NORTH AMERICA 51 



P. REGULARIS Kofoid, 1914, p. 38, PI. VII. Colony solid, 

 flattened, orbiculate, the peripheral cells broadly cuneate, the 

 other cells squarish in surface view of the colony, 10-15 A* wide ; 

 each cell with a slight external projection. The only species, 

 found in a fresh water reservoir at Berkeley, California. Fig. 15. 

 C. A. Kofoid. 



The peculiar arrangement of the cells is better understood by 

 the figures than by description. The colony may be considered 

 as a sphere much compressed in the line of the polar axis, the 

 two polar groups of four cells each coming in contact, the equa- 

 torial cells forming a ring, fitting into the groove around the 

 group of eight, "like an automobile tire into the rim of the 

 wheel," in the words of Kofoid. 



Page 173, for Key to the Species of Sorastrum, substitute, 



i. Outer angles of cells rounded, each with 2 spines. 2. 



i. Outer angles ending each in a short, conical point. 



2. S. bidentatum. 

 2. Cells as long as broad or longer. 3. 6". americanum. 



2. Cells broader than long. i. 5". spinulosutn. 



After description of S. SPINULOSUM, add, 



Var. HATHORIS (Cohn) Lemmerman * ; Selenosphaerium 

 hathoris Cohn, 1879, p. 13, PI. XI, figs. 16-17. Cells 16-20 ft 

 wide, 10 [i. high and thick, central body more distinct than in 

 the typical form. Pa., West. Europe. 



After description of S. BIDENTATUM, add, 



3. S. AMERICANUM (Bohlin) Schmidle, 18993, p. 230, fig. 6 ; 

 Selenosphaerium americanum Bohlin, 1897, p. 40, PI. II, figs. 

 38, 41. Cells as long as broad or longer, obcordate or obpyra- 

 midal, with stout gelatinous stipe attaching to distinct central 

 body of colony ; cells 8-15 X 6-8 \L ; colony 22-60 \L diam., with- 

 out spines. Wis., G. M. Smith. Europe, So. America. 



Page 175. Cancel paragraph beginning "The European 

 D. Luna/us" and substitute, 



2. D. LUNATUS A. Braun, 1855, p. 44; Rabenhors f , 1868, 

 p. 36, fig. 7. Inner cells ovoid-ellipsoid, outer lunate; cells 

 10-20 p. long, colonies up to 100/4 diam. Wis., G. M. Smith; 

 Fla., Borge. Europe. 



After paragraphs referring to DICTYOCYSTIS, add, . ' 

 *Fide Brunnthaler in Pascher, 1915, p. 201. 



