182 BRITISH DESMIDIACE.E. 



upper part of sides suddenly converging and slightly 

 retuse, upper angles rounded, apex broadly truncate, 

 straight or slightly retuse. Side view of semicell 

 elliptic-ovate. Vertical view elliptic, ratio of axes 

 about 1 : 1'8. Cell-wall smooth. Chloroplasts axile 

 with one pyrenoid. 



Zygospore unknown. 



Length 40-50 p ; breadth 27-35 //, ; breadth of 

 isthmus 11-13 ^; 



EXGLAXD. Westmoreland! (Bissett). T\ r . Yorks. 



WALES.- -Xear Bodorgan, Anglesey ! 



SCOTLAND.- -Xear Rhiconich, Sutherland ! 



lEELAND.--Gralway ! Dublin and Wicklow (Arclier.) 



Geogr. Distribution. France. Germany. Galicia 

 in Austria. Hungary. Italy. Portugal. Norway. 

 Sweden. Denmark. X. and S. Russia. Finland. 

 Siberia. Greenland. Central China. Japan. India. 

 Ceylon. Burmah. Sumatra (form). New Zealand 

 (var.). Australia. Central and E. Africa. United 

 States. Brazil. Paraguay. Patagonia. 



Despite its world-wide distribution the form of C. Hammeri 

 described by Reinsch as " A. majns ' ' is a very rare British 

 Desmid. This form we regard as the type of the species,, and 

 it possesses an elliptical vertical view with no trace of a 

 median inflation. 



Var. homalodermum (Xorclst.) nob. (PI. LXII, 



figs. 22, 23.) 



Cosmarium pyramidatum Breb. forma intermedia Nordst. ~N"orges Desm. 



1873, p. 19. 

 Cosmarium homalodermum Nordst. Desm. Arctoee, 1875, p. 18, t. 6, f . 4 ; 



Desm. Ital. 1876, p. 34 ; Wolle, Desm. U. S. 1884, p. 81, t. 17, f . 19, 20 ; 



Cooke, Brit. Desm. 1886, p. 82, t. 36, f. 7 ; De Toni, Syll. Algar. 



1889, p. 1043 ; West, Alg. N". Yorks. 1889, p. 292 ; Alg. N. Wales, 1890, 



p. 288 ; Eoy & Biss. Scott. Desiii. 1894, p. 104 ; Norclst. Index Desm. 



1896, p. 141. 

 C. homalodermum Rordst. var. rotunClatum'WilLe, Ferskv. Alg. N"ov. Semlja, 



1879, p. 36, t. 12, f . 18. 

 Ursinella homaloderma Kuntze, E,evis. gen. plant. 1891, p. 924. 



Cells rather larger, sometimes shorter ; vertical view 



slio'htlv tumid at the middle on each side : side view 

 ti 



of semicell more ovate (sometimes subspherical) ; cell- 

 wall thicker, very finely and often indistinctly punctate. 



