7-1: DESMIDS OF THE UNITED :.TATES. 



C. HOLMIEXSE, Lund. Plate XIX, fig. 23. 



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

 ately constricted, sinus narrow linear; semi-cell subquadrate, 

 sides straight or subcouvex, slightly converging until near 

 the somewhat dilated apices ; ends obsoletely crenulate ; 

 dorsum truncate-undulate, angles rounded. Viewed from 

 the vertex elliptic with the poles obtuse-angled ; side view 

 rectangular-elliptic ; membrane smooth. Chlorophyl homo- 

 geneous or in a single mass. 

 Diameter 33 //. ; length 63 yw. 



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

 Differs slightly from Lundell's figure in the crenulations, 

 and in being less restricted near the ends. 



Tar. INTEGRUM, Lund. Plate XIX, figs. 24, 25. 



Differs from the typical form in having no crenulations 

 nor plications near the apices, and no undulations on the 

 ends. 



Diameter 32-36 ja. 



Mountain spring, Rockdale, Pa. 



C. ANSATUM, Kg. Plate XIX, fig. 22. 



Cells twice as long as broad; constriction wide but not 

 deep ; semi-cells have a flat base, rounded lower angles, sides 

 converging, concave ; ends truncately rounded ; membrane 

 punctate ; end view oval. 

 Diameter 28-31 pi. 



Ponds, Pennsylvania, rather rare. 



Scarcely separable from a variety (fig. 28) of C. Holmiense, 

 except by the punctate membrane and the usually wider 

 sinus ; the latter is not correctly represented in fig. 22, should 

 be two or three times wider and not quite so deep. 



C. PYEAMIDATUM, Breb. Plate XVII, figs. 16, 17. 



Cells scarcely twice as long as broad, suboval ; constric- 

 tion deep, linear; semi-cells pyramidal, rounded at basal 

 angles, sides convex, gradually converging to the somewhat 

 truncate ends ; punctate ; end view broadly elliptic. 



Diameter 50-85 yu. 



A common species found probably in every State of the 

 Union. 



Var. STENONOTUM, Xord. Plate XVII, figs. 18, 19. 



This subspecies is separated from the typical form by the 

 shape of the sides of the semi-cells, which are somewhat 



