68 DESMIDS OF THE UNITED STATES. 



C. VENT/STUM, Rab. Plate XVI, fig. 37. 



Length of cell equal to about 1 diameters; constriction 

 deep ; sinus narrow linear ; semi-cells have a flat base, rounded 

 lower angles, sides somewhat convergent ; each with two 

 notches of equal size; ends truncate, and slightly retuse. One 

 chlorophyl mass in each semicell ; membrane smooth. 



Diameter 24-30//. 



Occasional in ponds, Pennsylvania and Now Jersey. 



C. Reinschii, Arch. (Dublin Microscopical Club). Plate XVI, 



fig. 12. 



Somewhat longer than broad, deeply constricted, sinus narrow 



linear; end- truncate; sides convex, erose dentate or notched. 



Membrane smooth; end view elliptic without a central in Hat ion. 



Diameter 30-35 /'-. 



Nut frequent, hut is found in Lake Hopatcong, N. J., and 

 in ponds, eastern Pennsylvania. 



C. Holmiense, Lund. Plato XVI, fig. 23. 



Cells twieo as long as wide, elliptic-rectangular, moder- 

 ately constricted, -inn- narrow linear; semicell subquadrate, 

 sides straighl or subconvex, slightly converging until near the 

 Bomewhat dilated apices; ends obeoletely crenulate; dorsum 

 truncate-undulate, angles rounded. Viewed from the vertex 

 elliptic with the poles obtuse-angled ; Bide view rectangular- 

 elliptic; membrane smooth. Chlorophyl homogeneous or in 

 a single mass. 



I tiameter 33 /'.: length 63 fi. 



Collected by F. H. Bosford, Mt. Mansfield, Vt., 1881. 

 Differs slightly from Lundell's figure in the crenulations, and 

 in being less constricted near the ends. 



Yar. INI!.', kim, Lund. Plate X V I , figs. 24, 25. 



Differs from the typical form in having no crenulations nor 



plication- near the apices, and UO undulation- on the end-. 



Diameter 32-36 fi. 



Mountain spring, Rockdale, Pa. 



C. AHBATUM, Kg. Plate XVI, fig. 22. 



Cells twice as long as broad ; constriction wide 1 nit not deep; 



semicells have a Hat base, rounded lower angles, sides eon- 



