lU FRESH-WATER ALG^ OP TUE UNITED STATES. 



Syn.—3I. rhnjens, Bailey, Microscopical Observations, pi. 1, fig. U: Smithsoniaa Contri- 

 butions, vol. ii. 



Hab Florida ; Bailey. 



Oblong, segments three-lobed, coarsely granulated near the edge ; basal lobes subdividwl by a 



deep notch into two rather broad and obtuse or slightly bidenlate projections ; terminal lobes 



exserted, emarginate ; extremities bidcntate or obtuse. 



* * Semicellulse quinque-lobatae. 



* * Semicelh b-lohed. 



W. truncatn, (Corda) Breb. 



M. magna, orbicularis, aut lisvis aut subtiliter punctata; scmicellulis quinqnelobis, lobis inter 

 se sinu obtusangulo subangusto discretis, basalibus et intermediis inciso-lobulatis, segmentis 

 acute bidentatis; lobo polari late cuneato, in dorso truucato, niodo leviter convexo, modo 

 leviter retuso, angulis aut bidentatis aut integris. (R.) 



Dwm.— 0.003" Long. .003G". 



Sijn. 31. truncata, (Corda,) Brebisson. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 



191. 

 Bab. — Georgia; Florida; Rhode Island; Bailey. Pennsylvania; Wood. Rhode Island 



(S. T. Olney); Thwaites. 



Frond orbicular, smooth ; segments 5-lobed ; basal and middle lobes obscurely bipartite, ex- 

 tremities bidentate ; end lobe very broadly cuneate, bidentate at the angles, and with a. slightly 

 central concavity. (A.) 



Itemarhs. — The dimensions given above yvexe taken from the largest specimens 

 I have seen, hut do not at all equal those given by Prof. Rabenhorst, his breadth 

 is .0011". According to the same authority, M. crenata, Breb., is merely a variety 

 of this species. 



Fig. 15, pi. 21, represents the outline of a frond of this plant. 



M. fiit'catn, Aa. 



M. perraagna paulo longior quani lata, levis ; semicellulis qninqne lobis (poene 7-lobis) ; lobis 

 omnibus rectis ; lobis basalibus angustioribus, bilobulatis, lobulis bifidis, sinu obtusangulo 

 vel acutangulo, segmentis liuearibus bidentatis (denticulis sajpe inasquilongis) ; lobis inter- 

 mediis duplo latioribus, inciso-bilobis, lobulis iisdeni ac loboruui basaliura ; lobo polar! non- 

 nihil anguste cuneato, prominulo, in apice plus minus profuude sinuato-vel undulato iuciso, 

 angulis bidentatis. 



Diam.—jl%^" = .008". 



Syn. — M. rolala, Ralfs, British Desmidieai, p. Tl. 



M. fui-cata, Agardii. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 191. 



Hab. — South Carolina; Georgia; Florida; Rhode Island ; Bailey. New Jersey; Wood. 



M. very large, a little longer than broad, smooth ; semicells 5-lobed (scarcely '7-lobed) ; lobes 

 all straight ; basal lobe narrower than the intermediate, bilobulate, lobules bifid, their sinuses 

 acute or obtuse, segments linear, bidentate ; teeth often long and unequal ; intermediate lobes 

 twice as wide as the basal, bilobate, their lobules of the same form as the basal lobe ; end 

 lobes narrowly cuneate, prominent, more or less profoundly sinuately or undulately cut at 

 the apex, angles bidentate. 



Remarhs. — According to Rabenhorst and others, tliere is a European form of 

 this species in which the marginal teeth are wanting. This may exist in this 



