SPONDYLOSIUM. 225 



cells oblong, with rounded ends, apex convex, but 

 flattened on the top ; in lateral view with rounded sides ; 

 vertical view subrectangular. sides nearly straight or 

 very slightly convex, ends rounded and produced, and 

 asymmetrical, there being a slight concavity on the 

 right side of the one produced end. and on the left side 

 of the other. Cells united into long twisting filaments. 



Zygospore unknown. 



Length lS'o-20^: breadth 28-33 u ; thickness 16- 

 19 (JL ; breadth of isthmus 20-24-5 u. 



Geogr. Distribution. Sweden. Italy. 



Var. triquetrum (Lund.) nob. (PL CLXVII, fig. 10.) 



Sp. pulclirum var. triquetrum Lund. Desm. Suec. 1871, p. 93 ; West, Alg. 

 W. Ireland, 1892, p. 116, t. 19, f. 3. 



Cells in vertical view triangular, angles obliquely 

 rounded-truncate ; chloroplast axile with a central 

 pyrenoid. 



Length 20-24 u ; breadth 28-36 ;JL ; breadth of isth- 

 mus 22-27(i. 



IRELAND.- -Lakes. Clifden to Roundstone, Galway ! 



Geogr. Distribution. Sweden. 



6. Spondylosium secedens (De Bary) Arch. 

 (PL CLXL figs. 8-11.) 



Sphcerozosma secedens De Bary, Conj. 1858, p. 7G, t. 4, f. 35-37 ; Rabenh. 



Flor. Europ. Alg. 1868, p. 150 ; Cooke, Brit. Desm. 1887, p. 5, t. 2, f. 3 ; 



Hansg. Prod. Alg. Bohm. 1888, p. 170 ; De Toni, Syll. Alg. 1889, p. 792 ; 



Roy & Biss. Scott. Desm. 1893, p. 10 : Liitkem. Desm. Millstattersees 



1900, p. 82, t. 1, f. 1-5. 

 Spondylosium secedens Arch, in Pritcli. Inf. 1861, pp. 719, 724 ; in Quart. 



Journ. Micr. Sc. 1871, p. 92 ; Eichler, Mater. Flor. Miedz. 1895, p. 57 ; 



West & G. S. West, Alga-fl. Yorks. 1902, p. 95 ; Alg. X. Ireland, 1902, 



p. 43, t. 2, f. 19, 20. 



Sphcerozosma excavation var. secedens Rabenh. Krypt.-fl. Sachs. 1863, p. 178. 

 Sph. pycjmceum Hauptfl. Zellm.u. Hiillgallerte Desm. 1888, t. 2, f. 24-26, 30. 



Cells small, about as long as broad, but sometimes 

 slightly longer or shorter, constriction moderately deep, 

 sinus open and obtuse ; seniicells subelliptical ; lateral 

 angles rounded, ventral margin slightly convex, dorsal 

 margin primarily strongly convex, but with a conspicuous 



VOL. V. 15 



