DesmidiecB.'] inftjsoeial animalcules. 275 



nor suture : but it is not luilikc the separated joints of a species of 

 Mougeotia, but the dilated truncate ends and roughness produced by 

 minute granules distinguish it. Length l-97th to l-64th. 



Docn)ixT.M coronation. — Stout : segments inflated at the base, and 

 bordered by tubercles at the end. 



Tliis species differs from D. nodulosim, which it otherwise re- 

 sembles, by ha%'iug the ends bordered with minute but distinct 

 tubercles. 



D. nodosum. — Stout; segments with four prominent nodes, sepa- 

 rated by constrictions ; end view crenate. It is one of the largest 

 species in the genus. 



D. constn'ctum. — Stout; segments with moderately deep constric- 

 tions, which separate four equal, gently ciu-ving prominences ; end 

 view entu'e. 



This species, says Dr. Bailey, is at once distinguished from D. no- 

 dosum, by the cross section of the nodes being a simple circle instead 

 of an indented one ; an end view of the latter proving each node to 

 be not a simple swelling, but really a whorl of tubercles. 



D. verrucosum. — Segments with numerous whorls of small pro- 

 minences, which give the margins an undulated appearance ; all the 

 imdulations equal. 



D. verticillaUim. — Segments with numerous whorls of tooth-like 

 projections; ends with three bidentate processes. 



These processes are so unlike what we find in other species of 

 JDocidium, that Dr. Bailey is disposed to fonn a new genus for the 

 reception of this species. 



D. crenulatuni = Closterium crenulatum (Ehr.) ; and is, according 

 to Bailey, identical with Docidmm nodulosum. 



D. hirsutum (Bailey.) — Segments many times longer than broad, 

 slightly inflated at base, surface hirsute. A small species resembling 

 D. Hhrenbergii va. form, strongly hii'sute on its outer surface. Lakes 

 in Florida, at Enterprise. 



D. xmdulatum (BaUey.) — Segments eight to ten times longer than 

 broad, constricted six to eight times at regular intervals throughout 

 their entire length, with the base and ends crenate. Smaller than 

 D. nodulosum, with more frequent and deeper constrictions. The same 

 characters distinguish it fr'om D. nodosum and D. constrictum. 



