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



Oscula small but very evident, in groups on the tops of the lobes ; diameter of each 

 about 1*5 mm. 



Skeleton. — There is no dermal skeleton present. The main skeleton is composed of 

 large oxeote spicules wliich, for the most part, form very stout but very loose Axinella-Wkti 

 fibres. The fibres all run more or less vertically upwards, but radiate somewhat from the 

 centre of the base. Numerous spicules also occur irregularly scattered between the fibres, 

 so that the whole skeleton becomes confused. 



Spicules. — Megasclera; of one kind only ; viz., large, smooth oxea, almost always 

 gradually and finely pointed at both ends, and slightly curved ; size about 0*87 by 

 0-022 mm. 



The systematic position of this sponge is very difficult to determine. The form of the 

 spicules would seem to indicate that it belongs to the Eenierinse, but the arrangement of 

 the skeleton places it amongst the Axiuellidse. Probably it belongs rather to the latter 

 group than to the former, and has simply lost the styli which form the most important 

 part of the skeleton in most Axinellids {cf. Axinella (?) lunwcharta, p. 186). 



The peculiar gelatinous or india-rubber-like ectosome marks it off from most hitherto 

 known species of either group, though it is more nearly paralleled in the Axinellidse than 

 in the Eenierinse {cf. Axinella, Acanthella). This unusual condition is due to an 

 enormous development of gelatinous mesodermal tissues, containing large stellate cells. 



Locality. — Inaccessible Island; depth, 90 fathoms. One specimen. 



Genus Ras2Ktilia,l>i urdo (Pis. XXXIX., XL.). 



1833. Raspelia, Nardo, Isis, p. 522. 



1847. Raspailia, Nardo, Prospetto della fauna marina volgare del veneto estuario, Venice, p. 3. 



Sponge long and slender, with a dense central axis of spiculo-fibre containing much 

 spongin, from which loose tufts of spicules radiate to the surface. Megasclera stylote 

 or subtylostylote, sometimes strongylote. Spined echinating styli sometimes present. 

 No microsclera. 



The most characteristic feature of this genus is the external form, taken in connection 

 with the absence of microsclera ; like Axinella, it is a difficult genus to diagnose, and 

 the two genera, as we have already indicated, come very near to one another. 



Raspailia tenuis, Ridley and Dendy (PI. XXXIX. figs. 2, 2« ; PI. XL. figs, 8, 8«, 86). 

 1886. Raspailia tenuis, Ridley and Dendy, Ann. and Mag. Nat. Hist., ser. 5. vol. xviii. p. 482. 

 Sponge (PI. XXXIX. fig. 2) of more or less erect growth (probably the branches 

 floated in the water), consisting of a very long, slender stem,^ giving ofi" at first 



' This description is taken from the larger of the two specimens, the smaller bears only a single branch. 



