7S DESMIDS OP THE UNITED STATES. 



C. SUBORBICUL.ARE, Wood. Plate XXIV, fig. 24. 



Cells small, a very little longer than broad, with the margin 

 irregularly crenate, or crenate-undulate ; semicells from the 

 side orbicular, from the vertex elliptical ; sinus very narrow, 

 but within somewhat excavated ; cytioderm thick, sparsely 

 coarsely granulated ; granules subdistant, in each cell arranged 

 in one or two curved marginal series and in a central group of 

 two or three short row-. 



Diameter 30 //..; length, 3-*> //. 



Saco Lake, New Hampshire, (Lewis). 



( '. AMnKMM, Breb. Plate XIV, figs. 5, 6, 7. 



Cell twice as long as broad, sides parallel, ends rounded; 

 constriction deep, linear ; -emicells rough with large, obtuse, 

 papilla-like pearly granules; side view much compressed, 

 about thrice as long as broad ; semicells contain two chloro- 

 pliyl nuclei. 



Yar. tumidum, W'ollc, has the side.-, front view, not parallel, but 



swollen or rounded. 

 Diameter 20-25 />. 



Rhode Island (Olney), Florida ( Baih\ . 



Frequent in Pennsylvania, New Jersey, Massachusetts. 



C. OBTH08TICUM, Lund. Plate XVIII, figs. 1. 5. 



< Jells -lightly more in length than the diameter, deeply con- 

 stricted, sinus narrow lineai-; semicells subelliptic, sides 

 rounded, base and dorsum nearly straight, coarsely verrucoses 

 verrucae in 68 vertical -cries; from the vertex elliptic, verru- 

 cose on and near the margins, area punctate; from the side. 

 circular. Chlorophyl nucleus single. 

 Diameter -211-81) a. 



Ponds, northern New Jersey and Mount Everett, Mass. 



( '. Ki.Kt.AN tissimim, Lund. Plate XIV, tigs. 8, 9. 



Cells two to two and one-half times longer than broad, 

 perfectly cylindrical, ends arched ; slightly constricted ; viewed 

 from the vertex, circular ; margin- verrucose-crenate ; mem- 

 brane with emarginate verrucae disposed in twenty-two longi- 

 tudinal series, of which about nine are visible in front view : 



