SPONDYLOSIUM. 223 



circular ; cell-wall smooth ; cells united into filaments, 

 not twisted, and destitute of a gelatinous sheath. 



Zygospores have been recorded, but without descrip- 

 tion.* 



Length 11 '5-19 *5 [/. ; breadth 12-25 k u. ; thickness 

 6-1 1 (JL ; breadth of isthmus 5-1 1 "5 p . 



ENGLAND.- -Plankton of Crummock Water, Derwent 

 Water, Bassenthwaite Water, and Thirlmere, Cumber- 

 land ! Plankton of Ked Tarn, Ullswater, Hawes Water, 

 Grasmere and Windermere, Westmoreland ! 



WALES.- -Llyn Ogwen, Carnarvonshire ! 



SCOTLAND.- -Plankton of Lochs nan Cuinne and Shin, 

 Sutherland!, of Lochs Luichart and Rosque, Ross!, 

 of Lochs Tay, Katrine, and Achray, Perth !, and Loch 

 Cuthaig, Lewis, Outer Hebrides ! 



IRELAND.- -Plankton of Mayo !, Galway ! and Kerry ! 



Geogr. Distribution.- -Xorway. United States and 

 Alaska. Canada. 



This species, considered for a long time to be a variety of Sp. 

 pulchrum (Bail.) Arch., was finally given specific rank in view of 

 its constant and distinctive characters. There is no possibility 

 of confusing it with any other species of Spondylosium, and it 

 has little, if any, relationship with Sp. pidchrum, differing in its 

 much smaller size, in its plane untwisted filaments, and in the 

 flattened closely applied apices of the semicells. The semicells 

 are of a different form from those of Sp. pulchrum, and the cells 

 are proportionately longer. It is a common species in the plank- 

 ton of many British lakes. 



4. Spondylosium papillosum W. & G. S. West. 



(PL CLXI, figs. 6, 7.) 



Sphcerozosma depressum West, Alg. N. Wales, 1890, p. 7 ; Schmidle, Alg. 



Bern. Alp. 1894, p. 87 ; Beitr. Alp. Alg. 1895, p. 9. 

 Spondylosium depressum Kirchn. Micr. Pflanz. Siissw. 1891, p. 21, t. 2, 



f. 61. 

 Sp. papillosum W. & G. S. West, Alg. Mad. 1895, p. 43, t. 9, f. 19 ; Notes 



Alg. I, 1898, p. 5 ; Alga-fl. Yorks. 1902, p. 95 ; Alg. N. Ireland, 1902, 



p. 43 ; Notes Alg. Ill, 1903, p. 10 ; G. S. West, Brit. Freshw. Alg. 1904, 



p. 176, f. 67 B (papillatum in error). 

 Sphcerozosma papillosum Schmidle, Alg. aus. Nyassa See, 1903, p. 75. 



* Lateral conjugation is reported by W. & G. S. West in specimens from 

 Maine (* Obs. Conj.' 1898, p. 54), but no description is given. 



