122 THE VOYAGE OF H.M.S. CHALLENGER. 
border being roughly jagged. Owing to the close and even arrangement of the septa 
the perforations are quite inconspicuous in a surface view of the corallum. 
Locality.—Santa Cruz Major Island, off Samboangan, Philippines, 10 fathoms. 
5. Cycloseris sinensis, Milne-Edwards and Haime. 
Cycloseris sinensis, Milne-Edwards and Haime, Cor., ii. p. 51. 
Four specimens, varying from 2 to 4 em. in diameter, were obtained. The species 
seems well characterised by the extremely thin and delicate corallum, much more thin 
and delicate than in any other species of the genus, nearly acute at the margin, with 
extremely fine costal striations and very thin, fragile, close, numerous, fenestrated septa. 
The columella is slightly developed and is very finely papillose. 
The form described by the Rev. J. E. Tenison-Woods as oceurring m Australia, and 
referred by him to this species, seems to be distinet from it, and appears to be more 
closely allied both to Cycloseris discus and Cycleseris freycinett. 
Locality.—Santa Cruz Major Island, off Samboangan, Philippines, 10 fathoms. 
6. Cycloseris discus, n. sp. (Pl. VI. figs. 3-3a). 
Corallum subcircular and thick, flat below, and nearly flat above, with the margin 
rounded and nearly as thick as the central part. Costee very fine and finely denticulate, 
scarcely distinct except at the marginal parts, and appearing like striations on the 
surface. Septa closely and evenly placed, not elevated, giving a very neat appearance 
to the corallum, extremely and thickly granulated and spinulous, with a jagged border, 
of six complete cycles, with a seventh more or less incomplete, and occasionally with 
rudiments of an eighth cycle; those of the first four or five cycles not fenestrated, but 
thick and equal, and of varying length according to the cycle to which they belong, 
swollen close to their point of origin, at which point they are rather thin and acute; 
those of the last two cycles extremely thin, and vertically fenestrated, with a divided 
edge, Axial cavity very deep, oblong and narrow, definitely outlined, owing to the 
inner edges of the septa being nearly vertical. Columella more or less well developed, 
papillose and granulated. 
Two specimens of this species were obtained; they form circular, thick and flattened 
disk-shaped coralla, which are from 2 to 2°5 em. in diameter, and from about 7 to 8 mm. 
thick at centre, and from 5 to 6 mm. thick at the margin. The species seems to be close 
to the fossil species Cycloseris semiglobosa (Michelin), the figure of which, given by 
Michelin, is useless for purposes of identification. The description of the fossil form, 
however, differs in many characters from the present species. 
Locality.—Santa Cruz Major Island, off Samboangan, Philippines, 10 fathoms. 
