134 
we propose here to name it Pleonosporium 
T ohyamanum in honour of Mr. Nobuo Toh- 
yama, director of the Fishery Experiment 
Station of Chiba prefecture, through whose 
kindness the authors have obtained many 
facilities for carrying out their phycological 
studies. 
SUMMARY 
1. In this paper is reported the discovery 
of four species of red seaweeds which are 
considered to be new to science and which 
belong to the genus Antithamnion and its 
allied genera in the family Ceramiaceae. The 
occurrence of an Australian species of the 
same group from the coast of Boso Peninsula 
near Tokyo Bay is also reported. 
2. New species here described are as fol- 
lows: Antithamnion hasisporum, Antitham- 
nion cristirhizophorum, Platythamnion hor- 
ridum, and Pleonosporium T ohyamanum. 
3. The occurrence in the northwestern 
part of the Pacific Ocean of Acroth amnion 
pulchellum J. Ag., which was originally re- 
ported from the west and south coasts of 
Australia in 1853, is established by compar- 
ing Japanese specimens with a fragment of 
Harveys original specimen collected at Port 
Fairy, Victoria. 
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