260 
THE VOYAGE OF H.M.S. CHALLENGEE, 
Section 2. Dirahdosa. 
Species possessing both cortical and somal oxeas, but only one form of trisene, which 
is neither an anatrisene nor a protrisene. 
Cydonium gibberosum (Bowerbank). 
Geodia gibberosa, Bowerbank, Proc. Zool. Soc. Lond., p. 7, pL i. figs. 16-22, 1873. 
„ ,, Carter, Ann. and Mag. Nat. Hist., ser. 5, voL ix. p. 362, 1882. 
Carter considers that Geodia tumulosa, Bowerbank, which he obtained from Puerto 
Cabello in the Caracas, is conspecific with Geodia caribou, Duch. and Mich., Geodia 
gibberosa, Lamarck, and Geodia tuberculosa, Bowerbank. 
Cydonium inconspicuum (Bowerbank). 
Pachymatisma inconspicua, Bowerbank, Proc. Zool. Soc. Loud., p. 326, pi. xxxi. figs. 1-6, 1873. 
Sponge. — Massive, sessile ; surface even, minutely hispidated ; cortex 0'556 mm. in 
thickness, composed almost entirely of the sterrastral layer. Pores in sieves fringed with 
marginal oxeas, overlying incurrent chones ; oscules not distinguishable from the pores. 
Spicules. — 1. Megascleres. 1. Somal oxea, 1’9 by 0‘029 mm. 2. Cortical oxea, 
0'39 mm. long (Bowerbank). 3. Orthotrisene, rhabdome 2'0 by 0'033 mm. 
II. Microscleres. 4. >S^erra5i5er, spherical, depressed ; 0‘064 mm. in diameter. 5 . 
Somal spheraster, centrum small, actines cylindrical, short, truncate, 0'0065 mm. in 
diameter. 6. Choanosomal oxy aster, centrum small, actions slender, about 0‘020 mm. in 
diameter. 
Colour. — Light fawn colour in the dried state. Size, 75 mm. long by 31 mm. and 
19 mm. 
Habitat. — South Seas. 
Cydonium nux, Selenka. 
Stelletta nux, Selenka, Zeitscbr. f. wiss. Zool., Bd. xvii. p. 569, pi. xxxv. figs. 11-13, 1867. 
Tetliya nux, Eidley, Spong. “ Alert,” p. 472 (footnote), 1884. 
Stelletta nux, Vosmaer, Bronn’s Thierreicb, Porifera, p. 319, 1887. 
Sponge. — Spherical, surface covered with tubercles, spicules scarcely projecting beyond 
it. Cortex thick. 
Spicules. — I. Megascleres. 1. Strongyle, fusiform, 1'83 by 0‘0387 mm. 2. Diclio- 
trisene. 
II. Microscleres. 3. Sterraster, oval, 0‘0774 by 0'09 mm. 4. Spheraster, centrum 
large, actines conical, smooth, oxeate, numerous ; diameter 0'096 mm., of centrum 0’0516 
