138 THE VOYAGE OF H.M.S. CHALLENGER. 
13. Fungia tenuidens, n. sp. (Pl. VI. figs. i-1@). 
Corallum irregularly elongated, rather thin, convex above, markedly trough-shaped 
below ; the central portion more or less flattened, solid, and seldom or inconspicuously per- 
forated, covered by distinctly radiated and sharply spinulose costee which become very 
distinct at the inclined margin. The growth at the margin more or less irregular, owing 
to the elongation and approximation of certain septa and the partial or complete sup- 
pression of others between them, with or without the union of the adjacent ones. Septa 
of very many cycles, very unequal in length, closely crowded and even, extremely thin 
and delicate, very flexuous, with their sides strongly granulated, especially in the smaller 
ones, and marked above by very minute serrations. The tentacular teeth very exsert 
and distinct, developed even in the last cycle, very thin, scarcely or not at all thicker 
than the septa, more or less rounded. Fossa elongated, rather narrow and deep ; colu- 
mella rudimentary. 
A single small specimen, which is from about 8 to 9 em. long, of this very distinct form 
was obtained. It must be placed close to Fungia conferta, Verrill. The very thin, 
delicate and flexuous septa, the very exsert and distinct but scarcely or not at 
all thickened tentacular teeth, the very irregular outline of the corallum, due to the 
unequal elongation of certain septa and the diminution or suppression of those between 
them, give a striking appearance to this species. 
Locality.—Ternate, Moluccas. 
Genus 2. Halomitra, Dana. 
Halomitra, Dana, Zoophytes, p. 341. 
This genus has lately been extended by Professor Duncan to include Podabacia of 
Milne-Edwards and Haime,' since, on the authority of those authors, it is stated that 
Halomitra differs from Podabacia simply in its general form, and in its unattached 
condition ;? characters which, as Professor Duncan points out, are not sufficient for 
generic separation. Between Halomitra pileus, Dana, and Podabacia crustacea, how- 
ever, there exist very important and striking differences apart from the simple difference 
in their habit, differences which entitle them to generic separation, and which were 
confounded by Milne-Edwards and Haime, owing to the fact that under the Fungia 
pileus, Lamarck (and under the Halomitra pileus of Milne-Edwards and Haime), were 
included two correspondingly distinct, but similarly-shaped, types of structure. 
The genus Halomitra, as defined by Dana, is certainly a well-characterised one ; 
and an essential part of the definition, which separates the genus from Podabacia, is 
derived from the nature of the wall and costz. In the definition given by Dana, the 
under surface is tersely stated to be “ stoutly and very crowdedly radiately echinate,” 
that is, the wall is solid and but very slightly perforated, while the costae form distinct, 
1 Journ. Linn. Soc. Lond. (Zool.), vol. xvii. p. 155. 2 Cor., ili. p. 20. 
