280 PERCY SLADEN TRUST EXPEDITION. 
3-4 cm. broad. One rather distorted specimen from the Red Sea is exceptional in 
having more raggedly toothed edges to its septa than any mentioned by Déderlein, 
individual teeth being 3 mm. long and having marked ridges below them on the septal 
sides. 
IV. Genus HALOMITRA. 
Dana, Zoophytes, p. 311, 1846; and M.-Ed, et H. Cor. iu. p. 20, 1860. 
I have had the opportunity of examining 12 specimens of this genus, five mentioned 
below from the Indian Ocean, collected by myself, a fragment from Samoa in the 
Cambridge Museum, referred to H. pilews, and six specimens in the British Museum. 
The genus was revised by Studer in 1901. He gave nine species, viz.; 1, H. fungites ; 
2, H. pileus; 3, H. tiara; 4, H. concentrica; 5, H. dentata; 6, H. philippinensis ; 
7, H. irregularis; 8, H. robusta; and 9, H. crustacea. For reasons already mentioned, 
the last must be removed as Podabacia crustacea from the family. No. 5 is Sandalo- 
litha dentata, Quelch, which I have already given my reasons for regarding as a Fungia. 
H. fungites appears to me to be obviously a young form, if it really belongs to the genus 
at all. For the rest, nos. 2, 8, 4, and 6 are characterised by smooth-sided, non-granulated, 
deeply toothed septa, and radiating rows of smooth costal spines. In these respects 
they differ markedly from H. irregularis and H. robusta, which I have removed to a new 
genus, Déderleinia. 
20. Halomitra philippinensis, Studer. 
Halomitra (Podabacia) philippinensis, Studer, Zool. Jahrb. xiv. p. 414, tt. 27 & 28. 
Halomitra philippinensis, Gardiner, Fauna and Geogr. Maldives & Laccadives, part iti. p. 492. 
Studer gives an account with figures of four species, which appear to me to be closely 
related, i. e. H. pileus (Dana), H. tiara (Agassiz), H. concentrica, Studer, H. philippinensis, 
Studer. They differ in that the three former have few pores extending through their 
walls, whereas the fourth is very perforate. All appear to have a central calicle with 
radiating secondary calicles, which have the septa around them somewhat elevated. 
These secondary calicles tend to be rather more crowded together and perfectly formed 
near the central calicles, and less crowded and perfect near the edges of the coralla. The 
septa in all are irregular (less so in H. concentrica), and the general tendency is for 
them to run from the central calicles to the edges of the coralla. They are, roughly 
speaking, alternately larger and smaller, but in this character again are very irregular, 
so that different parts of any corallum show a wide range in the proximity of their septa 
to one another, ¢. ¢. in the number which would be cut across in 1 cm. The septal 
edges are deeply toothed, especially deeply and irregularly in H. tiara and H. philip- 
pinensis. All have somewhat radiating costee which are clearly marked by smooth 
pointed spines, judging from the descriptions perhaps smallest in H. philippinensis. 
The five specimens before me, all of which are much perforated, I refer to Halomitra 
philippinensis, Studer. They evidently belong to the same species, though the three on 
which I identified the species as belonging to the Maldivan Region differ from my two 
new specimens from the Chagos Archipelago in being much less mitre-like (one Chagos 
