428 Wisconsin Academy of Sciences , Arts , and Letters. 
26. *S. quadricauda (Turp.) de Breb. 
XX. Cells naviculate, in lateral contact in 
middle third only. 
27. S. opoliensis Richt. 
b. Colonies with linear interstices between cells. 
28. S. perforatus Lemm. 
1. S. oahuensis (Lemm.) nov. comb. (PI. XXV: Fig. 1). 
S. quadricauda var. oahuensis. Lemmermann, 1905A, p. 630; 
PL VIII, Figs. 4-5. Lemmermann, 1900C, p. 335. (as S. quadri¬ 
cauda var. insignis West and West.) 
“Coenobium 2-16 cellulares, tegumento hyalino, mucosa 
circumvelatum. Cellulae 2 costis lateralis instructae, 
apivibus et lateralibus 1-4 aculeis fragilibus, granulosis 
armatae. Costae subtiliter granulatae. Membrana cellu- 
larum poris minutis densissime instructae.” 
Description of a gelantinous sheath in the genus Scenedes- 
mus is confined to this single species described by Lemmer¬ 
mann. The number of supplementary spines in addition to 
those on the four corners of the coenobe is variable. 
2. S. obliquus (Turp.) Ktz. (PL XXV: Fig. 7. PL 
XXIX: Figs. 63-68). 
Kiitzing, 1833, p. 609. de Brebisson, 1839, p. 271. Meneghini 
1840, p. 208. Ralfs, 1848, p. 192; PL XXXI, Figs. 15A-15C. 
Bailey, 1851, p. 29. Bailey, 1855, p. 12. Griffith and Henfrey, 
1856, p. 565; PL X, Fig.,5L Archer, 1857, p. 40. Spencer, 1882, 
p. 296. Griffith and Henfrey, 1883, p. 679; PL XIV, Fig. 51. 
Lagerheim, 1883, pp. 64, 66. Wille, 1884, pp. 10, 45. Griffith and 
Henfrey, 1885, p. 686; PL X, Fig. 51. Hansgirg, 1886, p. 116. 
Nordstedt, 1888, p. 19. Hansgirg, 1889, p. 132. de Toni, 1889B, 
p. 566. Hansgirg, 1890A, p. 112. Hansgirg, 1891, p. 317. Lem¬ 
mermann, 1891, p. 148. Hansgirg, 1892B, p. 120. Lemmermann, 
1893, p. 524. Schmidle, 1893A, p. 13. de Wildemann, 1893A. 
de Wildemann, 1893B, p. 91. Lemmermann, 1895A, p. 41. 
Lemmermann, 1895B, p. 296. West and West, 1895, p. 83. de 
Wildemann, 1895, p. 26. Borge, 1896, p. 7. Schroder, 1896, p. 
46. West and West, 1896, p. 381. Farlow in Trelease, 1897, p. 
196. Lemmermann, 1897, p. 108. Schroder, 1897C, p. 45. Stroh- 
meyer, 1897, p. 6. West and West, 1897B, p. 500. de Wildemann, 
1897A, p. 61. de Wildemann, 1897C, p. 78. Lemmermann, 
1898G, p. 249. Mez, 1898, p. 149; PL IV, Fig. 166. Schorler, 
1898, p. 38. Schroder, 1898, p. 24. Tilden, 1898, p. 26. Zacharias, 
