Sketch of the hifusoria of the family Badllaria. 289 



by several writers* to a "curious pinnatifid appearance" which 

 this species presents " before the uUimate separation of the joints." 

 I have not seen the filaments in this state, nor have I met with 

 any detailed account of this change in the few works which I 

 have been able to consult. 



This species is extensively diffused in Europe, and appears to 

 be equally so in this country. I have met with it from Rhode 

 Island to Ouisconsin, and south to Virginia; it occurs at West 

 Point in great abundance in ditches and peat bogs, where I have 

 found it most abundant in early spring. I believe Desmidium 

 cylindricum of Greville to be merely a state of this species. 



2. Desmidium hexaceros, Ehr. (Compare figs. 2 and 3, PL 1.) Cor- 

 puscles binary, trilateral, the points drawn out to three horns and trun- 

 cate at the extremity, -^-g of line. 



3. Desmidium aculeatum, Ehr. (Compare figs. 4, 5, and 6, PI. 1.) 

 Corpuscles spiny trilateral, the points drawn out to three truncate horns, 

 often terminating in three spines. 



I copy Ehrenberg's description of the two last species, that 

 they may be compared with the figures referred to above, which 

 represent various binary triangular bodies, some of which agree 

 pretty well with the above characters. They however are so 

 unlike D. Schwartzii, and present so many points of resemblance 

 to Euastrura that I shall describe them as species of that genus. 



Staurastrum. 

 Free, a simple univalve quadrangular carapace. 



1. Staurastrum paradoxum. Corpuscles rough, single or binary, 

 four setaceous horns in form of a cross. 



Micrasterias Staurastrum, Micrasterias tetracera, didicera, tricera. 

 Kutzing, Linnea, Vol. viii, p. 599, PI. 20, figs. 83, 84, and 85. 



St. paradoxum, Meyen, Nov. Act. Nat. Cur., xiv, p. 777, PL 43. 



" Formed principally of two cells united end to end, and each ter- 

 minated by cross-shaped prolongations, on which are perceived vestiges 

 of articulation." See Ferussac's Bulletin, June, 1830. 



I am not sure that I have yet met with this species in America; 

 I have, however, often seen the binary bodies represented by figs. 

 3 and 4, PL 1, having four arms instead of the three represented 

 in our drawing. In the four-armed state they agree closely with 

 the above characters of S. paradoxum^ as well as with Kutzing's 

 figure 83. 



* See Jlgarilh. Systema Algarutn, p. 15, and Greville in British Flora, VoL v, p. 402. 

 VoL xLi, No. 2.— July-Sept. 1841. 37 



