FRESH-WATER ALG^ OF THE UNITED STATES. 155 



enormiter hexagonis, angulis in processus rectos et divergentes productis, dorse processibus 

 similibus 4-5 instructo; semicellulis a vertice polygonis Tel suborbicniaribus marglne proces- 

 sibus numerosis, plerumque 9 instructo ; dorse processibus 5-8 instractis ; processibus omni- 

 bus similibus, granulato-dentatis, apice achreo simplicibus, bifurcatis vel fissis. 



Diam. — A vertice cum processibus, ts%\s" — -00475". Sine process. t/tW = -002". 



Syn. — St. munitum, Wood, Proceed. Ac. Nat. Sc, 1869. 



Hah. — In lacu Saco, New Hampshire ; (Lewis) Wood. 



S. rather large, about one-half longer than bread, slightly constricted in the middle ; semicells 

 from the front irregularly hexagonal, the angles prolonged in straight divergent processes, 

 and the surface furnished with four or five similar ones ; semicells from the vertex polygonal 

 or suborbicular, the margin furnished with numerous processes, mostly about nine, and also 

 with 5-8 on the dorsum ; processes all similar, granulate-dentate, their transparent apices 

 simple, bifurcate or torn. 



Remarks. — This species is most closely allied to St. furdgerum, Breb., from 

 which it is at once distinguished by the orbicular vertex. The constriction between 

 the semicells is also very different. In St. munitum it is a gradual, not very deep, 

 hour-glass contraction ; in St. fwrdgerutn it is very narrow and linear. 



Fig. 13 a, pi. 13, is a front view of this plant magnified 260 diameters ; fig. 13 6, 

 the end view of the same. 



St. enstephannm, (Ehrb.) Raxfs. 



St. laterum integrorum angulis productis apice spinulosis, spinnlarum furcatarum corona media 



dersali. (R.) Species tnihi ignota. 

 Syn. — Desmidium eustephanum. Ehrenberg, Verbreitung und Einfluss der Mikresk. Lebens 

 in Slid- und Nord-Amerika, t. 4, f. 23. 

 Staurastrum eustephanum, (Ehrb.) Ralfs, British Desmidiese, p. 215. 

 Stephanoxanthium eustephanum, Kutzing. Rabenhorst, Flora Europ. Algarum, Sect. 



III. p. 221. 

 Staurastrum eustephanum, Ralfs. Rabenhorst (loc. cit.) 



Safe.— West Point, New York ; Bailey. 



End view triangular with six emarginate spines on the upper surface ; each angle terminated 

 by a short ray tipped with spines. (Ralfs) 



St. senarinm, (Ehrb ) Ralfs. 



Antecedent! simile sed laterum parietibus spinulis furcatis binis (sex), corona dersali senaria. 

 (R.) Species mihi ignota. 



Syn. Desmidium senarium, Ehrenberg, Verbreitung. T. IV. 



Stephanoxanthium senarium, Kctzinu. Rabenhorst, Flora Europ. Algarum, Sect. III. 



p. 220. 

 Staurastrum senarium, (Ehrb.) Ralfs, British Desmidiese. Rabenhorst, (loc. cit.) 



Segments smooth in end view with three angles, each terminating in a short process tipped by 

 minute spines, without lateral processes, but with six others confluent at their bases on the 

 upper surface, divergent and forked. (Archer.) 



Genus XANTHIDIUM, Eheb. 



Cellnlse singulae vel geminse concatenatse, inflato-rotundatse, profunde constrictse ; semicellulse 

 compressEe, oblongs, hemisphsric* vel subquadrangulares, centre in tuberculum rotundatum vel 

 truncatum et denticnlatum protuberantes, ex transverse oblongo-rotundat*. Cytioderma firmum 

 setis, acnleis vel spinis simplicibus aut bi- tri-furcate-divisis armatum. Massa chlerophyllacea 

 radiatim expansa. Zygosperae armatee. (R.) 



