EUASTKUM. 117 



distinct lobules, each furnished with, usually, two horizontal 

 or diverging spines. Somewhat larger. 

 Diameter 35-40 /u. 



E. INTEGRUM, Wolle. Plate XXXI, figs. 18-22. 



Another form nearly allied to the above three species or 

 varieties; separated by the absence of the lower constriction 

 of the semi-cell. Size variable, diameter 16 3<> /u. 



The preceding four forms are closely related, and may be 

 accounted mere varieties. They are frequent. Having for 

 comparison, scores of sketches made of plants from as many 

 localities in different States from Vermont to Florida and 

 westward to Minnesota, this division suggested itself as the 

 most feasible and natural. I retain the old names, but with 

 somewhat modified diagnosis. 



The same is described as E. simplex, Des. U. S., p. 106. 

 Since the publication of the diagnosis, F. Gay, of Montpellier, 

 France, is found to have anticipated the adoption of the 

 same name for another Enastrumform. Hence we substitute 

 E. integrum for E. simplex. 



E. BINALE, (Turpin), Ealfs. Plate XXXI, figs. 23, 24. 



Cells minute, about one-half longer than broad, oblong- 

 oval; semi-cells with their basal portions entire; slightly 

 contracted beneath the ends ; apex dilated, its central notch 

 acute, broad, gaping. Transverse view with two lateral in- 

 flations ; ends truncate, angles rounded. 

 Diameter 15-25 //. 



Plants of this species have features in common with E. 

 integrum, but may be readily recognized by the proportionately 

 shorter form and the pouting separation of the end. 



E. cdMPACTUM, Wolle. Plate XXXI, figs. 28, 29. 



Very small, suborbicular, little longer than broad ; semi- 

 cell broad, transversely oval ; apex a slight protubenmce 

 with a linear incision ; two small prominences, one on cadi 

 side of the apical projection. 

 Diameter 20-22 /x ; length 28 /u. 

 Pond, Pennsylvania. 



E. OBTUSUM, Wolle. Plate XXXI, fig. 31. 



Minute, twice as long as wide ; semi-cells obovate, base 

 flattened, sides somewhat diverging, end broadly rounded 

 with linear incision in the center. 

 Diameter 14 //. ; length 25 yw. 

 Ponds, Pennsylvania. 



