48 
THE VOYAGE OF H.M.S. CHALLENGER. 
Tetilla radiata, Selenka. 
Tetilla radiata, E. Selenka, Ueb. einen Kiesel-Scbwamm v. acbtstrahligem Ban, &c., Zeitschr. 
f. wiss. Zook, Bd. xxxiiL p. 467, pi. xxvii., 1880. 
Habitat. — Eio de Janeiro ; depth, 3 fathoms ; bottom, blue-black mud. 
Remarks. — Selenka distinguishes this sponge from that which he identifies with 
Tetilla euplocamus, 0. Schmidt, by its smaller size, rose-red colour, and thinner oxeate 
spicules, which are from O'OOS to 0*01 mm. in diameter. Its chief excurrent canals show a 
tendency to a radiate arrangement in multiples of four (4x2); but though eight thus 
usually occur, seven and nine have also been observed. The sexes are distinct, but 
multiplication also takes place asexually by budding. 
Tetilla ridleyi, n. n. 
Tetilla dactyloidea, Ridley, Voyage of the “Alert,” p. 625, 1884. 
Sponge (?), an imperfect specimen, 40 mm. in diameter. 
Spicules. — I. Megascleres. 1, Oxea, fusiform, 2'5 by 0‘026 mm, 2. Protrigene, 
rhabdome 0’004 mm. in diameter; cladi 0‘07l mm. long. 3. Anatrigene, rhabdorae 
0’004 mm. in diameter; cladi 0'045 mm. long, chord 0'06 mm. 
II. Microsclere. 4. Sigmaspire, O’Oll mm. long, rarely becoming toxospiral, then 
O'OIG mm. long. 
Habitat . — Glorioso Islands, low water (Eidley). 
Remarks. — This sponge is very different to that from Mergui which Carter has named 
Tetilla dactyloidea, as I judge from a comparison of specimens. It would appear also, 
from Carter’s description, to differ considerably from the sponge to which Carter first 
applied the name “ dactyloidea." 
The ectosome is not furnished with a special skeleton, but attains a considerable 
thickness, about 0’7 mm. ; it consists of soft fibrous tissue, charged with what appear to 
be pigment-cells. The surface is thickly hispidated by spicules, of which the outer ends 
are broken off ; they appear, however, to be oxeas. Trisenes appear to be rare, those from 
which the measurements were taken were situated wholly within the sponge, the cladome 
lying just below the outer epithelium. 
Tetilla robusta (Carter). 
Tethya cranium, var. robusta, Carter, Ann. and Mag. Nat. Hist., ser. 5, vol. xi. p. 367, 1883. 
Sponge more or less spherical ; ectosome perforated by apertures about 10 mm. in 
diameter, which lead into large irregular roundish cavities, lined by a smooth membrane. 
