COSMARI17M. i i 



cately rounded, or frequently slightly retuse in centre ; margins 

 densely crenated ; viewed from the vertex, elliptic, from the 

 side, obovafce. Membrane densely verrucoee, verrucae large, 

 depressed, arranged in subregular or c sentric series. 



I tiameter 52-70 p. 



Hitherto have found this variety only in eastern Pennsyl- 

 vania. The original of the species was found in northern 

 Sweden, and described by 0. Nbrdstedt; it bears a resem- 

 blance to C. BotryHs and C. tetraopfUhalmum, but differs in 

 the form of the verrucae which arc short cylindrical truncate ; 

 in tetraophthalmum the verrucae are triangular hemispherical 

 obtuse, and iii C. Botrytii triangular with subacute api< 



( ". i'mimiwim. Archrr. Plate XIV, figs. 12-14. 



( Jells about one-third longer than broad, deeply constricted : 

 semicells oval, remote, separated by a wide sinus; isthmus 

 about one-fourth the diameter <>t' the cell, membrane granular. 



I Kameter 25- :;.". y. 



Prequenl in ponds, Pennsylvania, New Jersey, Afaasachu- 

 tts, Minnesota and Connecticut 



( '. orbiculatum, Ralfs. Plate \ | \'. 6gs. 20, 21. 



Twice a- long as wide; semicells spherical, connected l>\ a 

 narrow isthmus : cytioderm covered with large granules. 

 Zygospore, according to Ralfs, orbicular, studded with large 

 verrucae. 



Diameter 20-33 >,. 



Met with it frequently in ponds of New Jersey and Penn- 

 sylvania. 



( '. excavatum, Nord. Var. duplo major, Lund. Plate LIII, 

 Cms. 1 I. 1". 

 Cells nearly twice a- Ion- as wide, constriction wide and 

 deep ; end view orbicular; semicells subspherical with trun- 

 cate base; verrucae of membrane, producing a crenulate 

 margin. 



I uameter 21-25 //. 



Not rare in ponds, Pennsylvania, New Jersey, etc. 

 Wille of Norway descrihes a form " eUiptica" most nearly 

 allied to ours in front view, but elliptical in end view. Nord.'s 

 and Lund.'s descrihed forms are orbicular in end view. 



