FRESH-WAT i: K ALG^E OF THE UNITED STATES. 149 



Hab. South Carolina ; (Ravenel) Wood. 



Smooth, small; sinus ample, obtuse angled (sometimes acute angled?); serairells elliptic (or 

 subtriangular ?), with the dorsum slightly convex, at the angles with a straight or curved 

 transparent spine ; frura tbe vertex triangular (or quadrangular ''.), angles often rounded, 

 wiili u suiuetiuies obsolete spine superimposed. 







It-nun-];*. This species was collected near Aiken, South Carolina, by Prof. 

 Ravenel, who found it forming with various diatoms and desmids a slimy mass in 

 A feebly rumiiiii; ditch. It agrees very well with the European form, except that 

 it is not so largo (at least the largest I ever measured did not come up to the 

 si/.e of their transatlantic brethren), neither does it appear to vary quite so much. 

 In the description, I have placed in brackets those characters in which the European 

 form varies, and the specimens I have seen do not. 



Fig. 18, pi. 21, represents outline of end of a scmicell, magnified 7;>0 diameters. 

 9, pi. 13, a front view, and 9 a the end view, of the living frond, magnified 

 diameters. 



St. nrittifVriim, i: AI.KS. 



St. Iteve, St. cuspidatum quodammodo simile, et eadem mnpiitudine sed isthmo destitntnm ; 

 semiccllulis tumidis, in media partc subrotundatis, latcraliter in lobum, basi constrictum, 

 a]>i(>e aristatum productis, lobis divergentibus, a verticc tri-quadrilobo-radiatis, radiis strictis 

 :niui(li.-iuniilms cruciatim dispositis, iuterstitiis profuude excisis. (11.) Species mihi ignoia. 



/>iVim. Incl. arist. 0.0014". (R ) 



Xyn. St.aristiferum, RALFS, British Desmidieae, p. 123. KABKNHORST, Flora Europ. Algarum, 

 Sect. III. p. 204. 



Hab. Georgia ; Rhode Island ; Bailey. 



Segments smooth, in f. v. prolonged at each lateral extremity intoamamillatc projection, which 

 is terminated by a subulate, acute straight awn, the awns divergent, e. v. with three or four 

 angles ; angles inflated muiaillate, terminated by au awn, sides deeply concave in the centre. 

 (A.) 



St. Lew isii, WOOD. 



St. Iteve ; Binn amplissimo, spinulo parvo armato et cum angnlo obtnso ; isthmo nullo ; semi- 

 cellulis a fronte late triangularibus, a vertice triangularibus et cum augulis nonnihil tumidis, 

 et rotundatis ; angulis spino maximo, robnsto, acuto armatis. 



Diam. Long. cum. spin. ,J O " = .0025"; lat. cum. spin. y^oVn" .00225". Sine spin. : long. 

 *," = .001666" ; lat. rf&g" .001666". Spin. : long. TS W' = -000666" 



SynSt. Levnsii, WOOD, Proc. Acad. N. S. 1870. 

 Hob. In lacu Saco; (Lewis) Wood. 



Smooth, with a very ample sinus, which is armed with a small spine and has a very obtuse 

 angle ; isthmus absent ; semicells from the front broadly triangular, from the vertex trian- 

 gular, with the angles somewhat tumid and rounded ; angles armed with a very large acute 

 robust spine. 



Remarks. This desmid is most closely allied to St. arwtifertim, Ralfs, but differs 

 from it in outline as seen from the front, there being no mamellation of the ends. 

 The spines in the sinuses are always wanting in the European species. 



Fig. 19, pi. 21, represents the outline of the end of a semicell, magnified 750 

 diameters. Fig. 11, pi. 13, represents the perfectly formed frond, magnified 750 

 diameters. 



