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THE VOYAGE OE H.M.S. CHALLENGER. 
Qxyaster, actines conical, oxeate, minutely roughened or spined, very variable in number 
and disposition, frequently reduced to one, with a second represented by a lateral terminal 
tylote, which is inclined to the axis of the actine so as to render the spicule retort- 
shaped ; diactinate forms also common, the two actines sometimes making an angle 
of 60° with each other, with the outer margin well rounded about the angle, and the 
inner margin angular, a single actine 0‘029 mm. in length. 
Habitat. — East Africa ; collection British Museum. 
Remarks. — This species is distinguished by the characters of the choanosomal 
oxyaster, and the irregular repeated dichotomosis of the dichotriaene. 
Cydonium depressum (Bowerbank). 
Geodia depressa, Bowerbank, Proc. Zool. Soc. Lond., p. 5, pi. i. figs. 9-15, 1873. 
Sponge. — Massive, sessile, surface even, minutely hispid ; oscules congregated, re- 
sembling the pores ; cortex 0'8 mm. in thickness, constituted chiefly of the sterrastral 
layer ; ectochrote very thin, traversed by cortical oxeas. 
Spicules. — I. Megascleres. 1. Somal oxea, 3T75 by 0‘046 mm. (B.) to 4‘28 by 0'06 
mm. (S.). 2. Cortical oxea. 3. Orthotrisene, rhabdome 4‘23 by 0'054 mm,, chord 0'5 
mm. (B.), and 4'0 by 0’097 mm. 4. Anatrisene, rhabdome 6'35 by 0'0127 mm, (B.), 
or by 0'0258 (S,), cladi 0T3 mm. long, chord 0T35 mm. (S.). 
II. Microscleres. 5. spheroidal, 0T3 mm. (B.), 0‘08 mm. (S.) in diameter. 
6. Somal spheraster, 0‘006 mm, in diameter. 7. Choanosomal oxyaster, actines not 
numerous, conical, 0'032 mm. in diameter. 
Colour. — Cream-white in the dried state. 
Habitat . — Dardanelles. 
Remarks. — The letter (B.) after a measurement signifies that it was taken from 
Bowerbank’s illustration, (S.) from type-slides in the British Museum. 
The sponge is so similar to Geodia gigas, 0. Schmidt, that I believe the two species 
will prove to be identical ; but as I have only seen dried specimens of Geodia depressa, 
Bowerbank, I hesitate to suppress it. 
Cydonium gigas (0. Schmidt). 
Geodia gigas, 0. Schmidt, Spong. Adriat. Meeres, p. 50, pi. iv. figs. 8, 9, 1862. 
Sponge. — Spherical ; surface finely hispid ; oscules congregated ; excurrent chones 
larger than the incurrent, but otherwise similar. Cortex 1 mm. thick ; consisting of a 
well-developed ectochrote 0’13 mm. thick, traversed by very numerous hispidating oxeas 
