116 DESMIDS OF THE UNITED STATES. 



E. PINGUE, Elf. Plate XXXI, figs. 1, 2, 3. 



Somewhat longer than broad; semi-cells three lobed, each 

 lobe globularly rounded : the polar loin- with a small notch; 

 side view oval with ends slightly truncate-crenate; end 

 and side views show a slight central inflation of semi-cells. 

 Isthmus about one-fourth the diameter of the cell. 



I Hameter 35-45 //. 



Ponds, Atlantic and Passaic Counties, X. J. Our plants 

 are often without the terminal notch, but otherwise so near 

 the form described by Elfving, I adopt the name he has given. 



E. NORDSTEDTIANUM, Wolle. Plate XXX, figs. 7-13; and Plate 



LXIII, figs. 13-15. 



Cells quadrangular-oblong, not quite twice as long as 

 broad; semi cells obscurely three lobed; basal lobes broad, 

 each divided in the middle by a rounded notch into two 

 lobules with tridentate or spinous ends ; end lobe short, more 

 or less einarginate, the two sides of the apex usually some- 

 what reflexed, with a subacute or rounded notch between ; 

 lateral margins furnished with two or three horizontal spines. 

 End, transverse and side views (Plate LXIII, figs. 13, 14, 

 r> rectangular, with broad, square, and more or less sinuate 

 sides and ends; angles dentate. 



Diameter 45-50 ;<.; length 70-75 //. 



Frequent in pond near Minneapolis, Minn. ; rarer in New 

 Jersey and Pennsylvania. 



E. ELEGANS, Kg. Plate XXXI, figs. 10-16; 25, 26. 



Oblong, one and one-half to two times as long as wide; 

 central constriction narrow linear: semi-cells with sides 

 somewhat converging, with a constriction near the truncate, 

 angular end. and another, often very slight, between this 

 and the base: ends divided by a linear or acute angled notch ; 

 side view oblong elliptic, apices acute-conic; end view oval 

 with central inflation. 



Diameter 18-36 n. Common. 



E. ROSTRATUM, Ealfs. Plate XXXI. tigs. 8, 9. 



Varies from the preceding in the protuberant, emarginate, 

 or angular ends having a prominent, horizontal spine on 

 each angle. 



E. SPINOSI-M. Kails. Plate XXXI, figs. 4-7, 17. 



Nearly allied to the two preceding, but separated by the 

 more decided lateral notch in the basal lobes forming two 



