118 DKSMIDS OF THE UNITED STATJ-.S. 



E. ABRUPTUM, Nord. Plate LXIII, figs. 21, 22. 



Cells one and one-halt' t iincs as long as broad ; constriction 

 deep, narrow linear ; semi-cells trilobed, lateral lobes some- 

 what protruding above the bas-, near the middle ; ends 

 truncately rounded and usually dentate or granulate ; end 

 lobe incised bifid, with exterior angles furnished with short 

 spines; transverse view rectangular with large central infla- 

 tion, end margin more or less undulate granulate, or some- 

 times retuse. 



Diameter 28-30 ^ ; length 40 ;/. 



Passaic County (Wood Lake), N. J. 



This species does not strictly conform to the description of 

 the author, but it has so much in common that with his con- 

 sent, I adopt the name he chose for his Brazilian plant. 



Genus, MICRASTERIAS, Ag. 



Cells simple, lenticular, deeply constricted in the center; 

 viewed from the front, orbicular, or broadly elliptical ; from the 

 vertex fusiform with acute ends. Semi-cells three to five lobed; 

 lateral lobes entire or incisely-lobulate; end or polar lobe entire 

 or sinuate or emarginate, and sometimes with angles produced 

 and bifid. 



In but few species have the zygospores been detected ; they 

 are large, globular and furnished with stout spines, which are at 

 first simple, then become branched at the ends. 



SECTION I. Cell circular; segments flve-lobed; lobes approximate, the end lobe 

 narrower. 



M. TORREYI, (Bailey), Ealfs. Plate XXXIV, figs. 1-8. 



Circular ; lateral lobes deeply incised, making two or three 

 subdivisions to each ; all more or less tapering, and acute or 

 bidentate at the extremities. End lobe narrow, not exserted, 

 dilated at apex, concave, angles taper into acute points or 

 spines. 



Diameter 250-300 yw. 



Frequent in ponds of Now Jersey, Mt. Everett, Mass., and 

 few localities in Pennsylvania. 



Often variable in the number and form of the subdivisions. 

 Plate XXXIV represents eight varieties, the result of multi- 

 plication by dividing. Compare Introduction, page 18. 



M. PSEUDOTORREYI, Wolle. Plate XXXVI, fig. 1. 



Large, circular, five-lobed; basal and intermediate lobes 

 bisected, sections more or less conical, ends deeply furcate; 



