Pacific Species of Antithamnion — TokidA and INABA 
125 
Fig. 7. Platythamnion horridum Tokida and Inaba, sp. nov.: a , apical portion of a frond, showing 
the growing apex; b, part of lower portion of a frond, showing the base of a branch, the lowest cell 
of which lacks the adaxial pinna ( 1 ) ; c, three pinnae laterales, showing pinnulae; d, tips of two ulti- 
mate ramuli. a, X 245; b and c, X 150; d, X 480. 
In: Sci. Rep. Tohoku Imp. Univ., 4th Ser. 
Biol, 3(4): 528, Fig. 22, 1928]). 
Syn. Callithamnion pulchellum Harvey. 
Some account of the marine botany of the 
colony of Western Australia. Trans. Royal 
Irish Academy, 22: 561, 1855; Phycologia 
Australis 5: Synoptic Catal., p. liv. no. 692, 
1863; J. Agardh, Sp. Alg, 3(1): 20, 1876; 
De Toni, loc. cit., 4(3): 1338, 1903; A. H. 
S. Lucas & Florence Perrin, The seaweeds of 
South Australia, II. The red seaweeds, p. 333, 
1947. {non Callithamnion pulchellum C. 
Agardh, Sp. Alg, 2: 175, 1828). 
Frond 5-10 mm. long, epiphytic on the 
thallus of Gelidium subcostatum, sparsely 
branched, partly repent, attached to the sub- 
stratum by means of rhizoids arising from the 
basal cell of the lower, and sometimes also 
upper, pinnae; lateral branches arising from 
the basal cell of the pinnae, axial cells of the 
branches 37-60 /x diam. and 1.2-3 times as 
long as broad below, 60-86 g diam. and 
2. 5-3. 5 times as long as broad above, and 
1-2 times as long as broad in the subapical 
portions, often provided with three pinnae; 
lateral pinnae opposite, 120-345 /x long, 
with opposite pinnulae on each segment ex- 
cept the basal; pinnulae simple or rarely once 
divided, attenuate but not acute toward the 
apices, composed of subquadrate cells slightly 
constricted at their septa, 10-20 /x diam. at 
the base, 5-10 /x diam. at the apical cells; 
