388 PERCY SLADEN TRUST EXPEDITION. 
Authentic specimens of it are preserved in the British Museum, and we have figures 
and a diagnosis of them awaiting publication. 
Since this note was written, an excellent diagnosis of Flabellaria luteo-fusca, Crouan, 
has been published by Mr. Howe (in Bull. Torrey Bot. Club, xxxiv. 1907, p. 513), who, 
presumably on the ground of external habit, follows Murray and Boodle (Journ. of 
Bot. xxvii. 1889, p. 239) and places it in Udotea. 
Hitherto the only plants of either species of Cladocephalus have been recorded from 
the West Indies alone, but we now propose to describe a third species which was 
collected by Mr. Gardiner in the Indian Ocean. Among Mr. Gardiner’s plants are 
several specimens which have all the appearance of a peltate Udotea (fig. 14), being 
green, zoned, and borne on a delicate stalk. An examination of their structure reveals, 
however, a labyrinthiform pseudo-cortex (figs. 15, 16) similar to that of C. scoparius 
and C. luteo-fusca. But while in these two latter species the lateral branchlets arise 
from a comparatively coarse main filament, 50 » broad, in our Indian Ocean plant the 
main filaments are only 25 « wide, and the contrast in size between them and the final 
dichotomies of the branchlets (fig. 16) is not nearly so marked as in the two other 
species. One of the most characteristic features of our plant is its peltate habit, 
resembling that of Udotea conglutinata f. infundibuliformis (U. infundibulum, J. Ag., 
and U. cyathiformis, Decne.); but in addition to having a very different structure, it 
is at once distinguished from that species in being uncalcified. The form of the cup 
is irregular, being lop-sided, much raised on one side and depressed on the other. 
The new species has a very slender stalk and a large frond, much in the proportion of 
U. conglutinata, whereas the two West Indian species have long thick stalks. 
We would point out that in the generic description of Cladocephalus (J. c. p. 569) the 
author describes the capitulum as thamnioid or scopiform and non-zonate. These 
characters are, however, of specific rather than of generic value; and we propose that 
the generic diagnosis should be amended in such a way as to admit the inclusion of 
other species which possess the structural character of Cladocephalus, viz., the intricate 
labyrinthiform pseudo-cortex. 
AVRAINVILLEA, Decaisne. 
28. Avrainvillea amadelpha, Gepp. (Plate 48. fig. 20; Plate 49. figs. 21, 22.) 
Syn. Udotea amadelpha, Mont. in Ann. Sci. Nat. 4 sér. t. vii. (1857) p. 186; De Toni, Syll. Alg. 
i. (1889) p. 509. 
Amirante, 30 fms. Coetivy, on reefs exposed at dead low tide. Saya de Malha, 
25 and 29 fms. Cargados Carajos, 47 fms. Chagos Archipelago: Salomon, on reefs 
exposed at dead low tide. 
Geogr. Distr. Western Indian Ocean. 
This species was considered by its author to belong to Udotea, in which genus it has 
till now always been placed, but as a more or less unknown member. The original 
plant was collected by Le Due at the Island of Galega in the Indian Ocean and was at 
some time divided, the larger part being preserved in the Decaisne Herbarium in Paris, 
while the smaller part found its way into Kiitzing’s Herbarium, now in the possession 
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