OOSMARITJM. 65 



C. 8INU08UM, Lund. Plate XVI, %. 2. 



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

 sinuses narrow linear, not widened outwardly ; semicells 

 quadrangular, equilateral, sides and apices somewhat retusej 

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

 brane smooth; isthmus one-third of the diameter of cell; 

 nucleus single. 

 Diameter 1618 //. 



Pond, Berkshire Mountain-, Mass. 



C. Meneghinh, Breb. Plate XVI, fig. 7. 



t'ell- l-l. 1 , times as long ;i- wide; constriction forms a 

 narrow linear sinus; semicells subquadrate, base straight, 

 apex flat, truncate or slightly concave ; sides straight or con- 

 cave, corners rounded, diagonally truncate or slightly retnse ; 

 single chlorophy] mass in each semicell. Very variable. 

 Kirchner makes three varieties 



a. genuinvm, with side- and ends and upper angles refuse. 



Diameter 20-22 ft. 



I>. angidosum, Rab., sides and end- straight, upper and lower 



angle- diagonally truncate. 



I diameter 1 8 fi. 



c. cone! mi a hi, Rab., more elongated, semicells nearly quad- 

 rilateral, all angles truncate, or rounded. 



Diameter !-:2o fi. 



Found frequently ; probably has a wide range north, south, 

 and west. 



C. POLYGONUM, Naeg. Plate XVI, fig. -'JO. 



Small, polygonal, about as long as wide, entire, sinus very 

 narrow; semicells hexagonal-oblong, angles subacute or 

 obtuse; apices straight or rounded; cytioderm smooth or 

 punctate. 



Diameter 15-20 ft. 



Ponds, New Jersey and Massachusetts. Not frequent. 



C. LUNATUM, Wolle. Plate XVI, fig. 16. 



( ells nearly as long as wide, circular, constriction deep and 

 forms a wide rounded or oval sinus; semicells Innately curved, 

 5 



