FRESH-WATER ALGvE OF THE UNITED STATES. 121 



P. con!!)tric(iim, (Bailey) 



D. subvalidum, laBve, latitudine 10-12 plo longius, medio valde constrictum, stricturae margine 

 noil prominente ; cruribus a basi tumida in apicem late truncatum uon attenuatis, i uudu- 

 latis. (R.) {Species mihi ignoia.) 



Syn. — Docidium constrictum, Bailey. Ralfs, British Desmids, p. 218. 



Hab. — Rhode Island, Bailey. 



" Frond stout, segment.? with moderately deep constrictions, which separate four equal, gently 

 curYing prominences ; end view entire. ' This species is at once distinguished from D. nodosum 

 by the cross section of the nodes being a simple circle instead of an indented one,' Bailey." 

 Ralfs. 



P. Terriicosiim, (Bailey) 



D. validum, granuloso-verrucosum, latitudine 10-12 plo longius, undulatum, apicibus integris 

 truncatis. (R.) {Species mihi ignota.) 



Syn. — Gosmarium verrucosum, Bailey, Araer. Journ. Sci. and Arts, 1846. 



Docidium verrucosum, Ralfs, Brit. Desm. p. 218. Bailey, Micr. Observ. p. 28. 



Hab. — Rhode Island; Bailey. 



" Segments, with numerous whorls of small prominences, which give the margins an undulated 

 appearance, all the undulations are equal. ' This is a very pretty species with a waved out- 

 line, caused by the slight projections, which are arranged in numerous transverse rings,' 

 Bailey." Ralfs. 



P. hirtmitum, (Bailey) 



D. spinuloso-hirsutum, medio valde constrictum, diametro 10-12 plo longius; cruribus et basi 

 et apice subdilatatis, truncatis. (R.) {Species mihi ignoia.) 



Syn. — Docidium hirsutum, Bailey, Micr. Observ. p. 36. 



Hab. — Florida; Bailey. 



" Segments many times longer than broad, slightly inflated at the base, surface hirsute. A 

 . small species resembling D. Ehrenbergii in its form, but strongly hirsute on its outer sur- 

 face." Bailey. 



Genus TRIPLOCERAS, Bailey. 



Cellulse singulas, rectte, valde elongatae, processus magnorum seriebus transversis armata;, utroque 

 polo trilobatae, lobis acute bidentatis. 



. Syn. — Triploceras, Bailey, Microscopical Observations, p. 37, Smithsonian Contributions, 1850. 



Cells single, straight, very much elongate, armed with transverse series of large processes, trilo- 

 bate at each end, lobes acutely bidentate. 



T. Terticillatiim, Bailey. 



T. cellulis subcylindricis, sed utroque fine leviter angustatis et nonnihil fusiformibus, modice 

 robustis, diametro 12-20 plo longioribus; processibus lateralibus robustis, magnis, apice 

 emarginatis. 

 Diam. — Cum process. ^^Jo" = -00146" ; sine process, -r^'/jo" = .00113". 



Syn. — T. verticinatum,BAii,T^Y. Microscopic Observations. Smithsonian Contributions, 1850. 

 Docidium verticillatum, Ralfs, British Desmids, p. 218. 

 Pleurotaenium verticillatum, Rabenhorst, Flora Enrop. Algar., Sect. III. p. 148. 



5a&.— Rhode Island, New Jersey, Georgia, Florida; Bailey. Saco Lake, (Dr. Lewis) Wood. 



Subcylindrical.but slightly narrowed at each end, and therefore somewhat fusiform, moderately 

 robust, 12-20 times longer than broad; lateral processes large, robust, with their apices 

 emarginate. 



16 June, 1872. 



