106 THE VOYAGE OF H.M.S. CHALLENGER. 



Desmacidon conulosa, Eidley and Dendy (PI. XXIII. f:gs. 5, 5a, 56, 5c; 

 PI. XXIV. fig. 2). 



1886. Desmacidon conulosa, Eidley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. 



p. 346. 



S^wuge (PI. XXIV. fig. 2) consisting, in the case of the larger specimen, of a tough 

 peduncle, expanding and dividing above into two broad, flattened, palmate lobes. 

 Height of specimen 94 mm.; thickness of the lobes 8 mm. Colour in spirit greyish- 

 yellow. Texture firm, tough, resilient. Surface rugose, owing to numerous, thickly 

 placed conuli, which project above the dermal membrane ; these are absent from the 

 peduncle. Dermal onembrane thin, delicate, transparent. Pores scattered. Oscula 

 small, about 1-5 mm. in diameter, numerous, scattered on both flattened surfaces and 

 a few along the upper margin of the sponge. 



Skeleton. — Composed of a coarse reticulation of stout spiculo-fibre ; the fibres being 

 formed of the oxeote spicules with only a very small proportion of uniting horny 

 substance. The main fibres run more or less vertically to the surface and there 

 terminate in compact, slightly divergent tufts of spicules — the conuli above 

 mentioned. 



Spicules. — (a) Megasclera ; of one kind only, viz., very stout, fusiform oxea 

 (PL XXIII. figs, 5, 5a), tapering gradually to a very sharp point at each end. Size 

 about 07 by 0-057 mm. These spicules occur loosely scattered in the soft tissues of 

 the sponge, as well as in the fibres. (b) Microsclera ; small palmate isochelaj 

 (PI. XXIII. figs. 5b, 5c), with large anterior palms and lateral palms only slightly 

 developed. Length about 0'032 mm. 



A great number of small, spherical, yellow embryos occur in the deeper tissues of 

 the sponge. 



This species exhibits a close relationship to Desmacidon compressa, Esper (Ehlers), 

 but difi"ers in the arrangement of the oscula, which, in Desmacidon compressa, are said 

 to be large and confined to the upper margin of the sponge. In the description of 

 Desmacidon compressa we find also no mention of the remarkable and very 

 characteristic conuli present in the Challenger species. This species forms a connect- 

 ing link between the more typical species of the genus and the subgenus Homceodictya, 

 and in some respects comes very near to Desmacidon {Homceodictya) grandis, nobis {vide 

 p. Ill), from the same locality. 



Locality. — Simon's Bay, Cape of Good Hope, 10 to 20 fathoms. One large specimen, 

 from which the measurements given above are taken, and one small one. 



