158 BRITISH DESMIDIACE^;. 



Length 40*5 n ; breadth 23 '2 /* ; breadth of isthmus 

 15*5 n ; thickness 20 '2 /LI. 



ENGLAND. --Near Bowness, Westmoreland ! 



This species is characterized by the curious excavated 

 sinus and by its relatively great thickness. We have seen no 

 living specimens of it. 



18. Cosmarium Phaseolus Breb. 

 (PI. LX, figs. 12-14.) 



Heterocarpella Phaseolus Breb. in Clieval. microscop. et iisage, 1839, 



p. 272. 

 Cosmarium Phaseolus Breb. in Menegh. Synops. Desm. 1840, p. 220; 



Ealfs, Brit. Desm. 1848, p. 106, t. 32, f. 5 ; Breb. Liste Desm. 1856, 



p. 131; Arch, in Pritch. Infus. 1861, p. 732; Rabenh. Flor. Europ. 



Alg. Ill, 1868, p. 166; Kirchn. Alg. Schles. 1878, p. 153; Wolle, Desm. 



U.S. ]884, p. 81, t. 18, f. 28-32 ; Cooke, Brit. Desm. 1886, p. 88, t. 37, 



f . 3 ; Hansg. Prodr. Algenfl. Bohm. 1888, p. 201 ; De Toni, Syll. Alg. 



1889, p. 1001 ; West. Alg. N. Wales, 1890, p. 288 ; Add. Alg. W. Yorks. 



II, 1891, p. 245 ; Alg. W. Ireland, 1892, p. 145 ; Alg. Eng. Lake Distr. 



1892, p. 725 ; "Boy & Biss. Scott. Desm. 1894, p. 171 ; Nordst. Index 



Desm. 1896, p. 199 ; West & G. S. West, Alg. S. England, 1897, p. 486 ; 



Alga-fl. Yorks. 1900, p. 70; Alg. N. Ireland, 1902, p. 33. 

 C. Phaseolus a. typicum Klebs, Desm. Ostprenss. 1879, p. 35. 

 Euastrum (Cosmarium} Phaseolus Gay, Moiiogr. loc. Conj. 1884, p. 59. 

 Ursinella Phaseolus Kuntze, Revis. gen. plant. 1891, p. 925. 



Cells small, as long as broad, deeply constricted, 

 sinus narrow with a dilated extremity ; semicells 

 rather narrowly reniform. Side view of semicell sub- 

 circular, with a slight protuberance at the middle on 

 each side. Vertical view narrowly elliptic, ratio of 

 axes about 1 : 2, with a small protuberance at the 

 middle on each side. Cell-wall minutely punctate. 

 Chloroplasts axile, with one pyrenoid. 



Zygospore globose, densely aculeate, aculei arising 

 from broad bases. 



Length 29-35 n ; breadth 26-36 /i; breadth of 

 isthmus 9-11 ^; thickness 19-22 /n; cliam. zygosp. 

 without spines 33 /<, with spines 47 M- 



ENGLAND.- -Westmoreland (Bissett). W., N., and E. 

 Yorks ! Middlesex ! Surrey ! Devon ! Cornwall ! 

 (Ealfs). 



WALES. Capel Curig ! (Cooke ^ Wills), Llyn Ogwen ! , 



