466 Wisconsin Academy of Sciences , Arts , and Letters . 
Volk, 1905, p. 65. West and West, 1905, p. 270. Fritsch, 1906, 
p. 205. Schorler, Thallwitz und Schiller, 1906, p. 247. Borge, 
1907A, p. 58. Borge, 1907B, p. 4. Buchanan, 1907, p. 81. Migula, 
1907, p, 655. Selk, 1907, pp. 57, 68, 73, 98, 103, 108. Teodoresco, 
1907, p. 130. West and West, 1909B, p. 184. Gugliemetti, 1910, 
p. 32. Klugh, 1911, p. 97. Borge, 1913, p. 60. Brunnthaler 
1913, pp. 168, 171; Fig. 18. 
S. caudatus var. abundans. Wolle, 1887, p. 172. Riabinine, 
1889A, p. 303. Riabinine, 1889B, p. 47. Snow, 1903, p. 391. 
Dorogoslaisky, 1904, p. 224. 
S. quadricauda var. hyper abundans. Gutwinski, 1890, p. 63. 
Schroder, 1879C, p. 45. Schmidle, 1900A, p. (111). Migula, 1907, 
p. 656. 
S. quadricaudatus var. abundans. Lemmermann, 1893, p. 524. 
S. caudatus var. hyperabundans. Bohlin, 1897, p. 23. Kaiser, 
1908, p. 163. 
S. quadricauda var. sctosus abundans. Volk, 1905, p. 65. 
Scenodesmus caudatus var. abundans. Conn and Webster, 1908, 
p. 35; PI. VI. Fig. 32. 
Cellulis ovatis vel oblongi-ovatis. Membranae cellularum 
terminalum cum aculeis in polis atque inter polos. Poli 
cellularum interiorum cum aculeis. Dimens. cell. 8x4, 
9x4, 10 x 4, 10 x 5, 11 x 5.5, 12 x 7 p. Long. acul. 4-7. 5 p. 
Supplementary spines on the middle of the terminal cells 
were noted quite early in the study of the genus, Ehrenberg 
(1838) figuring a colony of his Arthrodesmus quadricaudatus 
with a median spine on each of the terminal cells, in addi¬ 
tion to the polar spines. Ralfs (1845) also gave figures of 
S. quadricauda (Turp) de Rreb. with the external cells 
having three spines and called it the variety /3, but gave it 
no name. Kiitzing (1849) established his Scenodesmus 
caudatus var. minor on the strength of Ralf’s figures, but the 
combination S. minor cannot be used to name this species 
since a S. minor has already been established by Kiitzing. 
Since S. caudatus forma abundans Kirch was the next name 
applied to this species the combination S. armatus (Kirch.) 
Chodat is the proper name. 
The number and position of the spines in the forms which 
I have isolated is quite variable. There are always the two 
polar spines on the terminal cells but there may be one spine 
(Figs. 133, 138) or there may be two to three spines (Figs. 
135, 139) in the middle of the cell. The two terminal cells 
of the same coenobe need not necessarily have the same 
