XAXT1IIDIUM. 7 : > 



Central area not protuberant, slightly thickened 

 and sometimes of a yellow colour; cell-wall smooth. 



Length without spines 48-54 p,, with spines 05-74 p ; 

 breadth without spines 3 6-39 /A, with spines -V>-55/x; 

 breadth of isthmus 11-1 '>//,; thickness k 25-oO p.. 



ENGLAND.- -Bo wness, Westmoreland ! 



i'. Distribution. India. Japan. United States. 



Var. spinuliferum West. (PI. CX, fig. 12.) 



X. crixtatu.m var. spini'liferum West, Alg. X. W ales, 1890, p. 291, t. 5, f. 21. 



Semicells furnished with 4 or 5 additional spines 

 irregularly placed just within the margin. 



Length without spines 45 p., with spines oS//.; 

 breadth without spines 36 p., with spines 48 p. 



WALES.- -Capel Curig, Carnarvonshire ! 



IRELAND. Lousrh Aunierin, Galwav ! 



o / 



Var. uncinatum Breb. (PI. CXI, figs, 2-4.) 



? Xanthidium bisenarium Ehreiib. in Pliysik. Abb. Preuss. Ak. d. wiss. zu 

 Berlin, 1841 [1843], pp. 334, 339, 390/426 [== Ev.astrv.m No. 11 Bailey 

 in Amer. Journ. of Science and Arts, iv, 1841, p. 296, t. 3, f . 13] ; Eabenb. 

 Flor. Em-op. Alg. Ill, 1868, p. 224. 



X. cristatum var. uncinatum Breb. in Ealfs' Brit. Desm. 1848, p. 115, t. 19, 

 f. 3d-f; Wille, Sydamerik. Algfl. 1884, p. 18 ; Cooke, Brit. Desm. 

 1887, p. 133 ; Be Toni, Syll. Alg. 1889, p. 923 ; Borg. Desm. Hrasil. 189i ., 

 p. 44; West, Alg. W. Ireland, 1892, p. 165; Alg. Engl. Lake Distr. 

 1892, p. 730; Eoy & Biss. Scott. Desm. 1893, p. 244; W. & (Jr. S. West. 

 Some X. Amer. Desm. 1896, p. 253. fig. xylogr. 3 ; Him, Desm. Finland. 

 1903, p. 23, t. 2, f. 34; W. \- (i. S. West, Brit. Fresbw. Phytoplanktoii, 

 etc., 1909, p. 180 ; Phytoplanktoii Engl. Lake Distr. 1909, p. 138. 



X. biseii'i ri.ii ni [forma typica' Turner, Fresbw. Alg. E. India, 1893, p. 99, 

 t. 12. f . 30 ; W. & Cl. S. West, Alg. N. Ireland, 1902, p. 30. 



Cells larger and proportionately a little longer ; semi- 

 cells widely subpyramidate Avith truncate apices, with 

 the 4 pairs of spines directed more vertically upwards ; 

 all the spines (single and paired) curved .or slightly 

 recurved, often dilated at the base; central area 

 slightly protuberant and furnished with a ring of 8-12 

 granules surrounding 3-5 central ones, more rarely 

 with a much more irregular granulation. 



Length without spines 55-74 p, with spines 7391 p, ; 



