FRESH-WATER A L G .E OF THE UNITED STATES. I47 



Si/n. — M. Jenneri, Ralfs, Biitish Desmidica;, p. 16. 



Uab. — Prope Philadelpliia ; Wood. South Carolina; (Ravenel) 



Large, oblong, for the most part finely granulate ; semicells 5-lobcd; lobes wedge-shaped ; basal 

 and intermediate, about equally broad ; end lobe broadly truncate or broadly rounded, in the 

 middle sometimes slightly and obtusely emarginate, sometimes rather deeply emarginate. 



Hemarks.—l have found this species near Philadelphia, and also received it from 

 Prof. Ravenel, by whom it was collected in South Carolina. The American plant 

 differs from the typical form in not having the ultimate lobules emarginate, they 

 being merely a little hollowed out in tlie centre, and sometimes scarcely this. The 

 angles in some specimens are also more acute. Mr. Archer, however, speaks of a 

 variety occurring in England, in which these lobules are not emarginate, and I do 

 not think characters can be found separating the American from the European 

 forms. Tlie median suture is in all the specimens very narrov/ and deep, a mere 

 line, as it were, "extending nearly to tlie centre. 



Eig. 7, pi. 13, represents a frond of this species. 



M. Torreyi, Bailey. *■ 



M. perniagna, oblongo-orbieularis, Isevis, profundissirae lobata; semicellnlis quinquelobis, lobis 

 basalibus profunde bifidis, laciniis infcrioribus apice bidentatis, suporioribus iutegris, lobis in- 

 termediis profunde trifidis, laciniis superioribus bidentatis, inferioribus integris, lac. omnibus 

 lanceolatis aciiminatis, inferioribus paulnm iueurvis, superioribus recurvis ; lobo polari non 

 prominente, e basi angusta seusim dilatato, iu vortice acute sinuato, augulis integris acumin- 

 atis. (R.) Species mihi ignola. 



Sijn. — 31. Torreyi, Bailey. Ralfs, Brit. Desmidiea?, p. 210. 



Hah. — Prope Princetown, New Jersey; Bailey. 



Frond smooth ; segments 5-lobed ; basal lobes bifid, middle lobes trifid, the subdivisions nearest 

 the opposite segments and those nearest the terminal lobe bidentate at the ape.x ; tlic inter- 

 mediate three terminating in acute points; all somewhat inflated and tapering ; terminal 

 lobe narrow, not exsertcd, spreading at the angles into divergent tapering points, ends 

 slightly emarginate. (A.) 



ITI. folinrea, Bailey. 



M. parva, subquadrata, Isevis; semicellulis trilobis, lobis lateralibus profunde bifidis (unde rec- 

 tior semicell. quinqueloba;), lobulis iiiiEqualiter inciso-dentatis, lobulis inferioribus rectis, 

 superioribus recurvis; lobo polari plus minus pruuiinento, anguste cuneato, in vortice plus 

 minusve emarginato, angulis aut acutis integris aut productis, bidentatis. R. S^^ecie.-i mihi 

 ignota. 



Syn. — M. foliacea, Bailey. Ralfs, Britii^h Desmidica;, p. 210. 



Ilah. — " Worden's Pond, Rhode Island; Bailey."' 



Frond subquadrate, smooth ; segments 3-lobed ; lateral lobes deeitly bipartite, inciso-dentale, 

 their margins concave, inciso-serrate ; end lobe broad, cuneate, and exserted, bi|)artite at the 

 angles, the subdivisions narrow, and minutely dentate at the extremities ; end concave. (A.) 



Genus STAURASTRUM, Meten. 



Cellulae libera natantes, in medio pins minus profunde constrietas ; seraicclhilfe a vortice 3-G angn- 

 lares vel radiatas. Cytioderma aut keve aut punctatum aut verrueosum aut aculeatum, nonnunquam 

 ciliis vel pilis obsessum. 



Cells swimming free, more or less profoundly constricted in the middle; semicells when seen 

 from the vertex 3 to fi angular or radiate. Cytioderm either smooth or punctate, or verrucose or 

 aculeate, sometimes covered with hairs or cilia. 



