70 DESMIDS OF THE rMTED STATES. 



C. OBSOLETUM, Eeiiisch. Plate LX, fig. 12. 



Cells elliptic, about one-fourth more in breadth than 

 length. Deeply constricted ; sinus rounded at the base, then 

 gradually narrowed towards tin- lateral angles of the semi- 

 cells, which come close together ; semi-cells in end view 

 elliptical; side view circular. Isthmus about one-third the 

 diameter of the cell. Membrane punctate or smooth : chlo- 

 rophyl concentrations or nuclei, two. 



Diameter 110 //. ; length 80 /<. 



I adopt Reinsch's name for this plant. In general form it 

 is the same; the two distinct nuclei also correspond, but in 

 size it is much larger and the angles of the semi-cells are not 

 at all or but slightly contracted. I collected it in a sluggish 

 streamlet, Ocean Grove, X. J. It is near C. Baileyi, but 

 differs in the form, of the sinus, and in having two nuclei in 

 each semi-cell ; it is also twice the size. 



C. EEGNESI, Eeiusch. Plate XLIII, fig. 4. 



Bare and of doubtful value. Has the appearance of a cell 

 of Sphaerozosma. 



C. SINUOSUM, Lund. Plate XIX, fig. 2. 



Twice as long as wide, rectangular, constriction not deep, 

 sinuses narrow linear, not widened outwardly; semi-cells 

 quadrangular, equilateral, sides and apices somewhat retuse; 

 end view subcircular: lateral view elliptic-oblong; mem- 

 brane smooth ; isthmus one third ox" the diameter of cell ; 

 nucleus single. 

 Diameter 16-18 /<. 



Pond, Berkshire Mountains, Mass. 



C. MENEGHINII, Breb. Plate XIX, fig. 7. 



Cells 1-1 i times as long as wide; constriction forms a 

 narrow linear sinus; semi-cells subquadrate, base straight, 

 apex flat, truncate or slightly concave; sides straight or 

 concave, corners rounded, diagonally truncate or slightly 

 retuse; single chlorophyl mass in each semi-cell. Very 

 variable. Kirchner makes three varieties : 



a. genuinum, with sides and ends and upper angles retuse. 

 Diameter 20-22 ju. 



b. angulosum, Eab., sides and ends straight, upper and 

 lower angles diagonally truncate. 



Diameter 18 /*. 



