98 DESMIDS OF THE UNITED STATES. 



as long as broad ; in the size being only three-fourths as large; 

 and especially in the peculiar lateral splitting, as it were, of 

 the basal lobes." 



In our observations, very few specimens of E. crassum 

 ever exceed two diameters in length ; they vary greatly in 

 size, and the " lateral splitting," a delusive appearance, is 

 common to all of them when the cells are empty. 



Saco Lake, New Hampshire, (Wood). 



E. OBLONGUM, (Grev.) Ralfs. Plate XXV, figs. 5, 6, 7. 



Cell smooth, oblong, semicells somewhat five lobed; lobes 

 nearly equal, cuneate; lateral lobes, or the basal only, with a 

 broad, shallow, marginal concavity : all their angles rounded ; 

 terminal lobe partly included between the lateral lobes, usually 

 with :i linear notch, sometimes tlii- is obsolete or very indis- 

 tinct. 



Diameter 6875 fx. 



This specie- La very variable, and if the end lobe, fig. 5, 

 were constant with the apex so broadly -innately excised, it 

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

 notch. The two forms, fig. 5 and fig. (!, are two distinct 

 varieties. 



Rhode [sland, New Jersey, Pennsylvania, Minnesota, and 

 other Stai 



E. multilobatum, Wood. Plate LI II, 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; semicells from the 

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

 basal lobe broadly emarginate, the central lobe obtuse, the end 

 lobe broadly and shallowly 3inuately emarginate; semicells 

 from the vertex five Lobed : cytioderm smooth. 



Diameter >>'2 >>.; length 1 _!< > ".. 



Saco Lake, New Hampshire 



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

 path. 



E. pinnatum, Ralfs. Plate KXVIII, figs. 1 I. 15, 16. 



Semicells five Lobed; end lobe exserted, dilated, upper 

 margin of all the lobe- nearly horizontal. The basal lobe- 



