140 THE VOYAGE OF H.M.S. CHALLENGER. 
as the Podabacia pileus (= Fungia pileus, pars), Lamarck (= Halomitra pileus, pars, 
Milne-Edwards and Haime). 
Halomitra tiara, Vervrill. 
Halomitra tiara, Verrill, Bull. Mus, Comp. Zo6l., Cambridge, U.S.A., vol. i. p. 53. 
A small specimen was obtained which seems referable to this species, though differing 
in many characters from the description of the adult form. It is about 6 cm. in 
diameter, irregularly concave below and convex above, with a single large, central parent 
ealicle, which becomes in the adult form indistinguishable from the younger ones which 
develop around it. The cost are scarcely distinct at the centre but they become more 
distinct with age, and the narrow, elongated, pointed, costal spines become larger. The 
calicles are often very crowded and separated only by a few, short, narrow plates which 
are often undivided and appear quite broad in comparison with the pointed and rather 
narrow septal teeth. Around the axial cavity the septa are often broad, being almost or 
quite undivided, but with age they become more divided, prominent and pointed. 
The species is very close to Halomitra pileus (Pallas), and may not be distinct from it. 
Locality.—Mactan Island, Philippines. 
Genus 3. Podabacia, Milne-Edwards and Haime. 
Podabacia, Milne-Edwards and Haime, Cor., iii. p. 19. 
The essential distinctions between Podabacia and Halomitra have been discussed 
under the latter genus. A not unimportant, additional point of difference between the 
two genera is to be found in the arrangement and dentation of the septa. In Podabacia 
the septa are evenly and closely placed, not markedly prominent around the fossa, while the 
teeth are small and do not give a markedly rough, irregular aspect to the corallum. In 
Halomitra the septa are markedly unequal, and very prominent around the fossa, while 
the teeth are very large, pointed and irregular, and give to the corallum a very rough and 
bristling aspect. 
As now understood the genus is extended to include unattached as well as fixed forms. 
It includes the following three species :— 
Podabacia crustacea (Pallas). 
Podabacia pileus (Lamarck). 
Podabacia robusta, n. sp. 
The last is founded on a specimen in the collection. 
Podabacia robusta, n. sp. (Pl. VI. figs. 5—5d). 
Corallum subcircular, or irregularly elongated, convex above and concave below, 
strong and thick. The under surface extremely perforated and marked by radial, 
