390 PERCY SLADEN TRUST EXPEDITION. 
is indeed a very handsome plant. The rhizome is cylindrical, is of considerable size, 
and is often encrusted with epiphytic animals; it arises obliquely or subvertically from 
the bulbous base by which the plant is attached. It rather suggests that the plant 
grew on a firm matrix covered with three or four inches of mud; and at its apex it is 
abruptly transformed into a short flattened green stalk, which bears the large round 
subauriculate membranaceous frond. The frond being thin shows clearly, when held 
up to the light, the zonate marking. When young and small the frond is quite entire; 
but in the old plants it is sometimes split here and there along the radii, so that it 
appears deeply and irregularly lacerate. The colour varies from a deep olive to a light 
green, while the rhizome is pale brown. In young fronds the base is rather cuneate, 
while in older plants it is often auriculate-cordate. 
The filaments of the frond are markedly torulose for some distance behind the apex 
(fig. 22), and do not taper towards their apices; the apices are often curled, but not 
markedly interwoven. 
A near ally to this species is Avrainvillea nigricans, Decne., from which it differs 
in having a short flattened stipes on a long unbranched rhizome and also a very thin 
green frond; its frond-filaments are of fairly uniform thickness (20-30 » diam.) and are 
much smaller than those of A. nigricans, which measure 60 » or more inside the frond, 
but diminish to 30 « at their apices. Further, 4. Gardineri is confined to the western 
Indian Ocean, being known only from Cargados Carajos, whereas A. nigricans is a 
West Indian species. 
A. Gardineri resembles A. amadelpha in being composed of filaments which for a 
certain distance behind the apex are torulose, but in .4. Gardineri the torulose beading 
is more regular, extends further back from the apices of the filaments, and the filaments 
are wider than those of 4. amadelpha. The pseudo-cortex, composed of twisted knotted 
apices, usually characteristic of 4. amadelpha is not found in A. Gardineri, though in 
the latter species the torulose apices are often curled and loosely intertwined. In habit 
A. Gardineri and A. wmadelpha are quite distinct. 
CHLORODESMIS, Bail. et Harv. 
30. Chlorodesmis comosa, Bail. et Harv. in Harvey, Nereis Bor.-Amer. iii. p. 29 (1858). 
Avrainvillea comosa, G. Murr. & Boodle, in Journ. of Bot. xxvii. 1889, p. 71, tab. 282. fig. 12; 
De Toni, Syll. Alg. i. 1889, p. 515. 
Hab. Seychelles: Praslin, on reef. 
Geogr. Distr. Fiji, Friendly Islands, New Caledonia, New Guinea, Celebes. 
Hawimepa, Lamour. 
51. Halimeda Tuna, Lamour. Classif. Polyp. corall. (1812) p. 186; E. S. Barton, 
Siboga-Expeditie, Monographe lx. Halimeda, 1901, p. 11, t. 1. 
f. typica, BE. 8. Bart., Coetivy reef. Saya de Malha, 26 and 55 fms. Cargados 
Carajos, 30, 45, and 47 fms. Chagos Archipelago: Egmont, lagoon shoal and reef. 
f. typica, E. 8. Bart., varying to f. platydisca, E.S. Bart., Cargados Carajos, 47 fms. 
[ 180 ] 
