114 DESMIDS OF THE UNITED STATES. 



E. DONNELLII, Wolle. Plate XXX, fig. 6. 



Broadly ovate, somewhat longer than broad, profoundly 

 constricted in the middle, sinus linear ; semi-cells trilobed ; 

 basal lobes orbicularly tumid ; terminal lobes semiorbicular ; 

 margin of each side armed with seven or eight short, stout, 

 conical teeth. Semi-cells with one larger central and four 

 smaller inflations ; three of them in a series on basal part, 

 and two on the end lobe. Cytioderm punctate. 



Diameter 38 yu. ; length 54 yu. 



Florida. Coll., J. Donnell Smith. 



E. FORMOSUM, Wolle. Plate XXX, fig. 16. 



Nearly twice as long as broad, oval in outline; semi-cell 

 with six marginal lobes, apices trifid, or tridentate ; central 

 tooth erect and the other two divergent ; the sections of the 

 two basal lobules more rudimentary than the others. Cytio- 

 derm smooth. 



Diameter 40 ^. ; length 62 yu. 



This plant bears some likeness to E. Nordstedtianum, but 

 is separated from it by the less prominent teeth, and especially 

 by the vertical position of the end lobules and the wide sinus 

 between them. 



E. DIVARICATUM, Lund. Plate XXX, figs. 18, 19. 



Cells one- fourth longer than broad, constriction deep, sinus 

 linear ; semi-cells subtriangular, gradually narrowing from a 

 broad base to a truncate apex ; sides undulate ; polar lobe 

 short, not dilated, linearly notched ; angles of the terminal 

 lobe, and of the basal lobe, armed each with a short aculeus ; 

 vertical view elliptic, middle of each side granulate dentate, 

 ends also dentate. 



Diameter 32-36 /x ; length 40-45 //. 



Occasional in ponds, Pennsylvania and New Jersey. 



E. POKORNYASUM, Grun. Plate XXXI, figs. 33, 34, 35. 



Semi-cells trilobed ; basal lobes, margins crenate or emar- 

 ginate ; terminal lobe erect, subcuneate, truncate, incised ; 

 membrane smooth. 



Diameter 17-20 //. ; length equal to two diameters. 



Rather common, often intermingled with the following two 

 forms which are so nearly allied, that it is almost impossible 

 to separate them. 



