182 PERCY SLADEN TRUST EXPEDITION. 
There seems to be a considerable correspondence as to the Lithothamnia in the 
Indian Ocean and large areas of the Pacific Ocean within the tropics. This concerns 
several of the species themselves as well as their mode of occurrence, peculiarly such as 
determine the general aspect of the vegetation. Thus the three reef-building species 
mentioned above occur at the Ellice Islands, one of them also at the Gilbert Islands, 
nearly under the same conditions as at the localities mentioned in the Indian Ocean. At 
the former islands Lithophyllwm onkodes is known from, e. g., “ reef-platform,” 
platform,” “ thick growth of nullipore from the shoals in the lagoon,” and “ consolidated 
rock, forming platform, Hurricane Beach” at Funafuti, from Fualopa and from Pava 
Islet. Lithophyllum craspedium partly grows gregariously with the former species or 
with Goniolithon frutescens, partly alone, e. g., “ocean-platform” Funafuti, and at 
Fualopa. Besides, at Onoatoa, Gilbert Island, it is “ a very abundant type and the most 
important reef-former,” no living coral haying been seen there, but ‘‘ everywhere on the 
lagoon and ocean-face immense masses”’ of this calcareous alga. Goniolithon frutescens 
occurs, é. g., on the ocean-platform of Funafuti, at Fualopa, and “is very abundant on the 
leeward (W.) islets of Funafuti Atoll.” It appears on the beach S. of the village, Funafuti 
lagoon, and on the lagoon-platform at Funafala. Here it is “ an important rock-former ” 
and it is “also an important reef-former.” Some species, however, which are common 
to both oceans seem to be more largely distributed in one than in the other, and as a 
matter of course there are several species which are as yet known only from one of these 
oceans, and which are rather local and seem to appear in no large numbers anywhere. 
Our knowledge of the occurrence of these calcareous alge in both oceans is, however, 
as yet so inconsiderable that at present no thorough comparison can be made which can 
lay claim to any particular interest. 
CORALLINACEA, (Gray) Harv. 
Tribe LITHOTHAMNIONEA, Fosl. 
Genus LiIrHoTHAMNION, Phil. (emend.). 
Subgenus EvuLirHoTHamMnion, Fosl. 
1. Lithothamnion purpurascens, Fosl. 
‘ Siboga’ Exp. n. Ixi. livr. 18 (1904), p. 18, in obs. 
Lithothamnion funafutiense f. purpurascens, Fos\. Corall. in Fl. Koh Chang, in Bot. Tidsskr. xxiv. 
(1901) p. 18. 
With some reservation, I refer a solitary specimen to the above species. It is 3-4.em. 
in diameter, and surrounds irregularly crust-like calcareous masses of some kind or other, 
with rather numerous excrescences mostly small and irregularly wart-like, some of which 
at least have risen owing to the unevenness of the substratum. It is rather richly furnished 
with conceptacles of sporangia, which are 400-700 » in diameter, and essentially agree 
with those of the species in question, intersected with about 100 muciferous canals. 
[ 98 ] 
*ocean- . 
