EUASTRUM. 107 



lobes, usually with a linear notch; sometimes this is obsolete 

 or very indistinct. 

 Diameter 68-75 /<. 



This species is very variable, and if the end lobe, flg. 5, 

 were constant with the apex so broadly sinuately excised, it 

 should be separated ; it is often incised with an acute-angled 

 notch. Tbe two forms, flg. 5, and fig. 6, are two distinct 

 varieties. 



Rhode Island, New Jersey, Pennsylvania, Minnesota, and 

 other States. 



E. MULTiLOBATUM, Wood. Plate LXIV, fig. 11. 



About twice as long as wide, profoundly constricted ; sinus 

 moderately large ; from the lateral view somewhat enlarged 

 and doubly biumbonate in the middle ; semi-cells from the 

 front trilobate, the lobes separated by very wide sinuses ; the 

 basal lobe broadly emarginate, the central lobe obtuse, the 

 end lobe broadly and shallowly sinuately emarginate ; semi- 

 cells from the vertex five lobed ; cytioderm smooth. 



Diameter 62 f^. ; length 120 m- 



Saco Lake, New Hampshire. 



This form, described by Wood, has not yet come across my 

 path. 



E. PiNNATUM, Ealfs. Plate XXXII, figs. 14, 15, 16. 



Semi-cells five lobed ; end lobe exserted, dilated, upper 

 margin of all the lobes nearly horizontal. The basal lobes 

 emarginate, and the intermediate ones smaller and entire. 

 Membrane punctate; terminal lobe with a linear notch. 

 Diameter 60-70 m- 



Meadow and mountain pools, Pennsylvania. 



E. HUMEEOSUM, Ealfs. Plate XXXII, figs. 12, 13. 



Semi-cells with terminal lobe dilated, emarginate, neck 

 sometimes partly included between the elongated lobes 

 which resemble processes ; basal lobes large, rounded, emar- 

 ginate. Cells smooth, two or three times longer than wide ; 

 notch of the end lobe indistinct, or short linear. 



Diameter about 75 m- 



Sluggish waters, Pennsylvania. 



If this form is not identical with Ralfs' figure, it is very 

 near it. The plant bears some evidence of relationship also 

 with H. crassum and with £. oblongum, and may possibly be 

 merely a variety of these. 



