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



si)icules, mainly arranged iDerpeudieularly to the walls of the smaller canals. The latter 

 spicules are mostly slender, slightly curved oxea ; sometimes they become blunted ; 

 average maximum size, 0'23 by 0'009 mm. 



Sincules. — Oxeote to strongylote, size variable {vide supra). 



We were at first inclined to refer this sponge to Rhizochalina singaporensis, Carter, 

 but closer examination shows certain well-marked diflferences, although in some respects 

 the two forms approach one another. Thus in Rhizochalina p)edunculata, the dermal 

 membrane contains a number of cylindrical spicules, some of which attain great size 

 {vide measurements), but which are, however, nearly or quite straight, while the deeper 

 spicules sometimes show a strong tendency to become blunted. In Carter's species there 

 are a great number of cylindrical spicules, but they are mostly very short, stout, and 

 strongly bent. 



The presence of a distinct peduncle (whence the specific name) may possibly be 

 regarded as characteristic, although, as there is only one specimen, it is impossible to say 

 whether it is a constant feature. 



It is perhaps noteworthy that a great number of the oxeote spicules of this species 

 show a tendency to become slightly rough and jagged at the points, suggesting the idea 

 that they have begun to undergo absorption (that is to say, as a vital process, not the 

 absorption occurring in dead spicules, which these are not). 



Locality. — Api, New Heljrides, 60 to 70 fathoms. 



Genus Oceanapia, Norman (PI. IX.). 

 18G9. Oceanapia, Norman, Brit. Assoc. Rep. for 1868, p. 334. 

 Microsclera (viz., sigmata) present. 



Oceanapia rohusta, Bowerbank, sp. (PI. IX. fig. 3). ' 



1866. Isodidya rohusta, Bowerbank, Mon. Brit. Spong., vol. iL p. 304. 



1866. Desmacidon Jeffreysii, Bowerbank, Mon. Brit. Spong., vol. ii. p. 347. 



1867. Gellius robushis, Gray, Proc. Zool. Soc. Lond., p. 538. 

 1867. ? Biemna jeffreysii, Gray, Proc. Zool. Soc. Lond., p. 539. 



1869. Oceanapia Jeffreysii, Norman, Last Rep. Dredging Shetland Isles, Brit. Assoc. Rep. for 



1868, p. 334. 



Sponge more or less globular, solid, with a number of tubular processes or jistulsB 

 coming off abruptly from all parts of the surface. Colour in spirit yellowish to nearly 

 white. Size (of the body) very variable. Fistidse 75 to 100 mm. long by 6 mm. wide, 

 closed at the ends, where they exhibit an irregular branching into four or five or more 

 short, finger-like processes, resembling the tubes of Rhizochalina. oleracea, figured by 

 Schmidt (Spong. Atlant. Gebiet., pi. iv. fig. 1). Texture in well-preserved specimens 

 firm and compact throughout. Surface smooth. 



