FRESH-WATER ALG^ OF THE UNITED STATES. 135 



Cells small, subelliptical, profoundly constricted in the middle, joined by translucent bands into 

 families ; semic61Is seen from the front elliptical, and nearly twice as long as broad, from the 

 vertex elliptical, from the side roundish ; sinus broad ; chlorophyl masses single in each cell ; 

 cytioderm thin, smooth. 



Bemarhs. — This plant was found by my friend Mr. Quiraby growing in a beau- 

 tiful spring above Camden, upon whose bottom it formed a gelatinous, trans- 

 lucent, greenish mass. The cells resemble in shape those of G. cucumis, although 

 much smaller. They are joined by bands into little families, in which the original 

 parent-cell is generally very distinct, it, or rather the two cells into which it first 

 divides, remaining in the centre of the group. The bands are so hyaline that their 

 edges can alone be distinctly seen, and hence the latter often look as though they 

 were threads — there appearing to be two parallel threads, or two threads crossing 

 one another, or a single thread, according as the band is flat, twisted, or on edge. 



It gives me great pleasure to dedicate the species to my friend Mr. Quimby, by 

 whom it was collected. 



Fig. 9, pi. 1, represents one of the family groups of this plant. 



Genus EUASTEUM, Eheb. 



Cellulae vel oblongae vel ellipticse, medio profunde incisse, symmetrice sinuatse, vel lobatae, tumori- 

 bus inflatis circularibus (rare obsoletis) instructae, utroque polo sinuato-emarginatae vel inciso-bilo- 

 batse, a vertice ellipticae. 



Cells either oblong or elliptic, profoundly incised in the middle, symmetrically sinuate or lobed, 

 provided with circular inflated protuberances (which are rarely absent), at each end sinuately emar- 

 ginate or incisely-bilobate, from the vertex elliptic. 



A. Ldbo polares in apice late isinuaiio-excisi. 



A. Polar lobe with its apex broadly sinuaiely excised. 



E. multilobatum, Wood. 



E. magnum, fere duplo longius quam latum, medio profunde constrictnm, et cum sinu modice 

 ample; a latere medio ventricosum et duplo biumbonatum, ad verticem dilatatum et emar- 

 ginatum ; semicellulis a fronte trilobatis, lobis sinus amplissimis inter se sejunctis ; lobi basale 

 distincte late emarginato, lobo centrale obtuso, lobo polare late leviter sinuato-emarginato ; 

 semicellulis a vertice quinque lobulatis; cytiodermate laevi. 



Diam.— Long. tiAtW' = -00475". Lat. ^^5"^^' = .0025". 



Syn. — E. multilobatum, Wood, Proc. A. N. S., 1869. 



Mob. — In lacu "Saco;" New Hampshire; (Lewis.) 



E. large, about twice as long as broad, in the centre profoundly constricted, with the 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, the basal 

 lobe broadly emarginate, the central lobe obtuse, the end lobe broadly and shallowly sinuately 

 emarginate ; semicells from the vertex five-lobed ; cytioderm smooth. 



Bemarhs.— The basal lobes of this beautiful desmid are distinctly five lobulate, 

 the lateral lobules being longer and broader than the others, which, instead of 

 being emarginate, are obtuse. The sinuses, separating lobes and lobules, are very 

 broad, with very obtuse angles. When the desmid is viewed from two-thirds 

 round, so as to show the anterior and posterior lobules especially, it presents an 



