EUASTRUM. 99 



emarginate, and the intermediate ones smaller and entire. 

 Membrane punctate; terminal lobe with a linear notch. 



Diameter 6070 ft. 



Meadow and mountain pools, Pennsylvania. 



E. humerosum, Ralfs. Plate XXVIII, figs. 12, 13. 



Semicells with terminal lobe dilated, emarginate, neck some- 

 times partly included between the elongated middle lobes which 

 resemble processes; basal [pbes large, rounded, emarginate. 

 Cells smooth, two or three times longer than wide; notch of 

 the end lobe indistinct, or short linear. 



Diameter aboul 75 fx. 



Sluggish waters, Pennsylvania. 



It' this form is nol identical with Kalis' figure, it is very 

 near it. The plant bears some evidence of relationship also 

 with II. crassum and with E. oblongum, and may possibly he 

 merelv a variety of these. 



E. ansatum, (Ehrb.) Ralfs. {K Ralfsii, Rab.) Plate XXV, 



figs. 8, 9, 10 j and I Mate XXIX. figs. 11, 12. 

 Semicells inflated at the base, and tapering upwards to the 

 notched hut nol dilated extremity ; end view cruciform. 

 Cytioderra punctate. There appear to he two distinct varieties 

 of this species, perhaps distincl plant- ; the one tw ice the size 

 of the other. 



Diameter normally 2536//. X'ar. major, Diameter 62 74 fi. 



Frequent in ponds ami quiet waters, widely distributed. 

 The various sizes may represent different stages of develop- 

 ment. 



E. didelta, (Turp.) Ralfs. Plate XXIX. figs. 9, 10. 



Cells rather more than twice as long as broad; semicells 

 pyramidal, inflated at the base and again at the middle; end 

 scarcely dilated, more or less rounded, notch linear; trans- 

 verse view show- four shallow lobes on each side and one on 

 each end. Cytioderm punctate. 



Diameter 2'2-'2'> ".; length 4554 '/. 



There is a .-mailer form which measures about onedburth 

 less. Specimens often very close to the following, K. ampul- 

 laceum. Transverse view nearly the same. 



Frequent everywhere, north, south and west. 



