REPORT ON THE TETRACTINELLIDA. 
329 
suffered an arrest of development. The oscules are surrounded with a slightly thickened 
margin, and sometimes one or more smaller accessory oscules occur in the same cloacal 
roof as the main centrally situated one. The cloacal roof is about 9 or 10 mm., and the 
oscule 1 mm. in diameter ; but in one instance out of the four present in one specimen 
it has become enlarged to 4 mm. in diameter at the expense of the cloacal roof. In this 
case the openings of the excurrent canals in the floor of the cloaca are fully revealed. 
This conversion of a cloaca with a small oscule to a wide superficial depression with an 
oscule as wide or almost as wide as itself is a phenomenon of very frequent occurrence. 
Discodermia japonica, Doderlein. 
Discodermia japonica, Doderlein, Zeitschr. f. wiss. ZooL, Bd. xl. p. 62, pis. v.-vii., 1884. 
Sponge. — Clavate or conical, in older examples once or oftener dichotomising ; 
oscules situated in the middle of the summit, or at the ends of the branches. Pores (?). 
Spicules. — I. Megascleres. 1. Desma, epactines of equal length, smooth, or with 
transverse crescentic ridges and tubercles, cladose, cladi ending in tubercles and other 
syzygial processes. Total length from 0'3 to O’S mm., of epactines OT to 0'5 mm., 
thickness near the centre 0’03 to 0T3 mm. 2. Discotriaene, to that oi Disco- 
dermia discifurca. 3. Oxea. 
II. Microscleres. 4. Microxea, fusiform, curved, smooth. 5. Microstrongyle, ellip- 
soidal, minute. 
Habitat. — Island of Enoshima, Bay of Sagami ; depth, 30 to 60 fathoms. 
Discodermia (J) leevidiscus, Carter. 
Discodermia Ixvidiscus, Carter, Ann. and Mag. Nat. Hist., ser. 5, vol. vi. p. 503, pi. viii. fig. 51» 
1880. 
Sponge. — Small ; surface even. 
Spicules. — I. Megascleres. 1. Desma (not sufiiciently characterised), syzygial pro- 
cesses expanded, irregular. 2. Discotrisene, depressed in the centre or cyathiform. 
II. Microsclere. 3. Microxea, minutely spined, 0‘034 mm. long. 
Colour. — Yellow internally. Size, about 6 mm. in diameter. 
Habitat. — Gulf of Manaar, Indian Ocean ; depth, under 65 fathoms. 
Discodermia {?) papillata, Carter. 
Discodermia papillata, Carter, Ann. and Mag. Nat. Hist., ser. 5, vol. vi. p. 146, pi. viii. fig. 48’ 
1880. 
Sponge. — Small, incrusting and burrowing ; surface even. Oscules and pores (?). 
Spicides. — I. Megascleres. 1. Desma, of the usual characters, covered with wart-like 
(ZOOL. CHALL. EXP. PABT LXIII. 1887.) RlT 42 
