I'KXIUM. 97 



Geoi/r. Distribution. Germany. Austria. Switzer- 

 land. Bornholm. Faeroes. Singapore. Java. Central 

 China. Brazil. 



This species is readily distinguished from P . polyrnorphum 

 ly its more cylindrical cells with more truncate apices. The 

 median constriction is also more evident in P. crassiusculum 

 and the cell-wall is smooth. The chloroplasts have also fewer 

 and more irregular longitudinal ridges. It is a much rarer 

 species than P. polymorphum, and one which we have never 

 seen in quantity. 



24. Penium curtum Breb. 

 (PI. X, figs. 21, 22.) 



Closterium curtum Breb, 1838. 



Cosmarium curtum Ealfs, Brit. Desm. 1848, p. 109, t. 32, f. 9 ; Breb. Liste 



Desm. LSoO, p. 133 ; Arch, in Pi-itch. Infus. 1861, p. 735 ; Eabenh. Flor. 



Europ. Algar. Ill, 1868, p. 176. 

 Penium curtum Breb. in Kiitz. Spec. Alg. 1849, p. 167 ; Nordst. Desm. 



Spetsb. 1872, p. 25 ; Wille, Ferskv. Alg. Nov. Semlj. 1879, p. 56, t. 14, 



f . 74 ; Wille, Norges Ferskv. Alg. 1880, p. 49 ; Eacib. Desmidyja Cias- 



tonia, 1892, p. 390 ; West, Alg. Eng. Lake Distr. 1892, p. 721 ; Eoy & 



Biss. Scott. Desm. 1894, p. 251 ; Nordst. Index Desm. 1896, p. 93 ; 



West & Gr. S. West, Alg. Madag. 1895, p. 47 ; Alg. S. England, 1897, p. 



479 ; Wehv. Afric. Freshw. Alg. 1897, p. 77 ; Furth. Contrib. Freshw. 



Alg. W. Indies, 1899, p. 283; Alga-fl. Yorks. 1900, p. 47; Alg. N. 



Ireland, 1902, p. 22. 

 Dysphinctium ? curtum Nag. Gatt. einz. Alg. 1849, p. 112 ; Eeinsch 



Algenfl. Frank, 1867, p. 178. 



Dysphinctium (Actinotxnium) Regelianum Nag. 1. c. p. 110, t. vi E. 

 Calocylindrus curt us Kirchn. Alg. Schles. 1878, p. 143; Wolle, Desm. 



U. S. 1884, p. 54, t, 12, f. 15, 16 ; Cooke, Brit. Desm. 1886, p. 126, t, 43, 



f. 11. 

 Cosmarium Thwaitesii d. curtum Klebs, Desm. Ostpreuss. 1879, p. 27. 



Cells small, sometimes minute, a little more than 

 twice longer than their diameter, with a distinct 

 median constriction; semicells attenuated, sides convex, 

 apex rounded and sometimes slightly thickened ; cell- 

 wall punctate ; chloroplasts with about eight longi- 

 tudinal ridges. 



Zygospore unknown. 



Length 22-60^; breadth 10'5-32'5/x; breadth of 

 isthmus 9'5-30/u. 



ENGLAND. Westmoreland ! W. and !S T . Yorks ! 

 Lancashire! Leicester (Roy). Gloucester! (Rolfs). 

 Surrey! Devon! Cornwall! (Ralfs). 



7 



