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PACIFIC SCIENCE, Vol. IV, April, 1950 
Fig. 5. Platythamnion horridum Tokida and 
Inaba, sp. nov.: a, middle portion of a frond, 
showing the mode of branching, pinnae laterales, 
pinnae transversales, and gland cells; b, the same, 
showing a tetrasporangium (1). a and b, X 150. 
known species of the genus, the main axis 
looks as if it bore verticillate spines on each 
segment, and the frond presents as a whole 
a quite spiny appearance. The specific name 
as well as the Japanese name is given with 
reference to this appearance. The frond is 
Fig. 6. Platythamnion horridum Tokida and 
Inaba, sp. nov. Type specimen. X 4. 
subdichotomously branched, and the branches 
often lack an adaxial lateral pinna on their 
lowermost cell. In these respects our species 
does not differ from other known species of 
Platythamnion (cf. Kylin, 1925: Fig. 34 a\ 
Tokida, 1942: Fig. 8 b). 
Acrothamnion pulchellum 3 J. Agardh 
Figs. 8; 9 a—e\ 10 a-f; 11 
J. Agardh, Analecta Algologica, p. 25, pi. 
1, figs. 6-10, 1892; De Toni, Sylloge Alga- 
rum, 6: 451, 1924 (nomen), (non Acrotham- 
nion pulchellum as interpreted by Yendo 
[Notes on Algae new to Japan, V. In: Bot. 
Mag. Tokyo 30 (355): 262, 1916} and by 
Yamada [Marine Algae of Mutsu Bay, II. 
3 In accordance with Article 61 of the Interna- 
tional Rules of Botanical Nomenclature the spe- 
cific epithet pulchellum is not available for trans- 
fer, since C. pulchellum Harvey (1855) was in- 
validated by C. pulchellum C Agardh (1828). 
