30 FRESH-WATER ALG^ OF THE UNITED STATES. 



Minnesota, not infrequent. 



This species reminds one of C. nasutum, Des. U. S. p. 89, 

 but that is proportionately shorter and strongly granulate. 



C. LOEVE. Comp. Des. U. S. p. 62. Plate XV, fig. 10. 



Duplicate specimens are represented, Plate LYII, figs. 

 35, 36. 



From a fountain in Pottsville, Penn., where they occurred 

 by thousands in gelatinous masses, August, 1880. 



C. OCULIFERUM, Lagh. Plate LXI, figs. 7, 8. 



Cells small, deeply constricted, sinus inwardly and out- 

 wardly more or less dilated ; semi-cells semi-circular-trian- 

 gular, ends retuse, sides slightly convex or straight, inferior 

 angles obtuse ; above the middle a single large granule and 

 below it a series of six small granules arranged in a semi- 

 circle, ends tending towards the retuse apex ; viewed from 

 apex oval, from sides sub- circular. Membrane smooth. 



Diameter of cell 24 /* ; length 32 JJL. 

 Pond, Tewksbury, Massachusetts. 



C. NORDSTEDTII, Delp. Plate LVII, figs. 23-25. 



Cell somewhat longer than broad, constriction deep ; 

 semi-cell rectangular-oblong about twice as wide as long, 

 granulate around the margins, center usually nude. 



I adopt this name for a form widely distributed, but vari- 

 able ; sometimes it resembles C. triplication in size and shape, 

 but differs in the number and arrangement of the granules, 

 which are not in series of threes, but in continuous eccentric 

 rows. Sometimes they cover the upper half of the semi-cell, 

 then again only one or two rows occur within but close to 

 the margin; the center and basal half are usually nude. 

 The sides are not so straight as figured by Delponte, but the 

 front and end views are always more or less rectangular- 

 oblong. 



Eeinsch has named a very different form C. Nordstedtii; it 

 is nearly, if not entirely, identical with C. cyclicum, Lund. 



C. EXCAVATTJM. (Y. Des. U. S. p. 77.) var. TRIGONUM, Lagh. 



Plate LX, figs. 24, 25. 



Cells in vertical view triangular, sides straight, or some- 

 what convex, angles rounded. 



Diameter of cells 18 JJL ; length 20 j^ ; thickness 18 /A. 

 Tewksbury, Massachusetts. 



