«4 



and armecl wilh too minute spines. Sides neaiiy parallel. Xear the 

 apex each is produced into a stDut serrate ray tipped with three 

 spines. Apex of semicell truncate, projecting above the rays and hea- 

 ring several serrations. End view triangular, sides concave, angles 

 drawn out into rays. Surface marked by several rows of serrations. 

 Around the centre of the semicell (in end view) six larger bifìd or 

 trifid projections. Dim. 44 « 5o-52 a. 



In demselben Jahre beschreibt auch Raciborski (Die Desmidieenfl. 

 d. Tapakoomasees in Flora Bd. 81, H. i) ein S. protractum und 

 zwar ein wenig frùher als Johnson^ weshalb die Art des letzteren 

 •einen anderen Namen bekommen muss. 



Arihrodesmus Michiganensis n. sp. p. 29Ó, f. 12. Sinus gaping, 

 broadly rounded, semicells being connected by a short neck. Semic. 

 subelliptical, with the apex of the celi drawn out into a broad trun- 

 cated lobe, and each end armed with a long slightly recurved spine. 

 In vertical view rhombic elliptical with a long spine at each end. 

 Side view circular. Dim. 3Ò-40 « 24-30 = 7-9 a; cr. 16-18 y.. 



Cosmocìadiiun tumidwn n. sp. p. 206, f 23. Cells usually joined 

 in fours by a hyaline, mostly unbranched filament. Greatest diameter 

 of celi placed at right angles to the connecting tilaments. Sinus 

 deep, linear; semicells hexagonal elliptic, with apex flattened. In ver- 

 tical view elliptical with slight but distinct median inflation. Side 

 view nearly circular. Dim 9«8« 2 j.; cr. 5 u.. 



Cosmariuni Facificum n. sp. p. 29Ò, f 25. Sinus strongly gaping. 

 Isthmus narrow. Semic. subelliptical. Sides curving regularly from 

 the base lo above the middle, then converging by a sharp angle 

 to form the rounded eud. End view elliptical, with no inflation. Side 

 view nearly circular. A single pyrenoid in each semicell, Membr. 

 punctate. Dim. 32-34 » 25-28 « 6 u.\ cr. i5-i7 ■/. 



C. dispersuìii n. sp. p. 207, f. iq. Sinus deep. narrowly linear. 

 Semic. semicircular. with the apex sometimes sligthly tlattened. Mar- 

 gin gently undulate with about eighteen clevations, often less distinct 

 toward the apex. End view elliptical; side view nearly circular. Two 

 pyrenoids in each semicell. Membr. finely punctate. Dim. 40 « 40-44 

 « I I u..; cr. 20 a. 



Cfr. Schmidle Zur Kritik ein. Sùsswasseralg. (La ISJuova Noi. 1897, 

 p. Ó7)! 



.\usserdem sind Formcn folgender Arten abgebildet: Penium an- 

 nidare West, P. Cylindriis v. silesiaciim Kirchn., Clostcrium maciila- 

 tuiii Ilast., C. angiLstatiuìi v, clavatum Ilast., C abniptum West, C. 



