72 DESMIDS OF THE UNITED STATES. 



primarily more or less densely aculeated; later the aculei 

 drop off and leave short granule-like stumps; end view 

 elliptical. 

 Diameter 33 //. ; length 30 p. ; breadth of constriction 10 //. 



Pond, Minneapolis, Minn. Collected by Miss E. Butler, 



1882 and 1883. 



C. SMOLANDICUM, Lund. Plate XIX, figs. 35, 36. 



Cells somewhat longer than wide; isthmus narrow, con- 

 striction deep, sinus narrow linear ; semi-cells semicircular 

 with straight base and arched back sometimes subtruncate, 

 angles (inferior) obtuse, mounted with a papilla ; end view 

 elliptical ; lateral view circular. Membrane distinctly punc- 

 tate. Chlorophyl masses two in each semi-cell. 

 Diameter, 34-48 //. 



Various localities, Pennsylvania and New Jersey. 



Usually the cells are about one-eighth longer than broad ; 

 they vary considerably in size. At Pleasant Mills, New Jersey, 

 there is a variety which is somewhat depressed, measuring 

 one-eighth less in length than breadth. The distinguishing 

 feature of this species is the papilla at each angle. 



C. EXIGUUM, Archer. Plate XIX, figs. 13, 14. 



Cells very small, smooth, oblong, H-2 times as long as 

 broad; medial constriction slight; semi-cells subquadrate, 

 'containing one chlorophyl nucleus ; ends obtusely rounded. 

 Diameter 12-15 js. 



Florida, collected by J. D. Smith, 1878. 



C. NOTABILE, Breb. Plate XIX, fig. 11. 



Cells small, about twice as long as broad, margins entire 

 or moderately undulate-crenate ; ends truncate; semi-cell 

 more or less pyramidal, base somewhat reniform, end broadly- 

 truncate; angles rounded, cytioderm smooth or finely 

 granulate. 



Diameter 22-28 ^ 



Ponds of eastern Pennsylvania. 



C. UNDULATUM, Corda. Plate XIX, fig. 20. - 



Cells 1* times as long as wide, ends broadly rounded,, 

 margins undulate ; deeply constricted, sinus gradually en- 

 larged outwardly ; semi-cells semi-orbicular ; sides and back 

 broadly rounded, margins undulate crenate, usually with 

 nine crenae to a semi- cell; cytioderm smooth. Zygospores 

 spherical, armed with long spines bi- or tri-fid at apices. 



Diameter 40-44 //. 



