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



yellow colour/ and in having slightly larger and decidedly stouter oxeote spciules (PL II. 

 fig. 12), which measure about 0'45 by 0-022 as against 0-4 by '01 9 mm. There do 

 not, however, appear to us to be sufficient differences to merit a distinct varietal name. 



Locality. — Station 208, January 17, 1875; lat. 11° 37' N., long. 123° 31' E. ; 

 Philippine Islands ; depth, 18 fathoms ; bottom, blue mud. One specimen. 



Habitat. — Port Darwin, North Australia (Ridley, " Alert ") ; Philippine Islands 

 (Challenger). 



Petrosia hispida, Ridley and Dendy (PI. II. fig. 16 ; PL III. fig. 2). 



1886. Petrosia Idspida, Eidley and Dendy, Ann. and Mag. Nat. ilist., ser. 5, vol. xviii. p. 327. 



Sponge (PI. III. fig. 2) massive, sessile, subglobular or lobate, narrowing towards 

 the base, bearing on the upper surface numerous smaU mammiform processes, each with 

 a single round osculum at the summit. The larger of the two specimens measures 62 mm. 

 in height by the same in breadth. Colour in spirit yellowish-grey. Texture firm and 

 fairly compact, rather brittle. Surface uneven, minutely hispid. Dermal membrane 

 difficult to make out, owing to the hispidity of the surface and the absence of a special 

 dermal skeleton reticulation. Oscula very conspicuous, numerous small round openings, 

 each on the summit of a volcano-like projection, remarkably constant in size, diameter 

 about 1'5 mm. Pores, rounded openings scattered through the dermal membrane. 



Skeleton. — No dermal reticulation. The main skeleton consists of a reticulation of 

 spiculo-fibre, the primary lines being fairly distinct (sometimes five or six spicules 

 broad), and running vertically to the surface, near which they are more distinct than 

 elsewhere, and having their terminal spicules projecting for a short distance beyond 

 the surface, thus causing the characteristic minute hispidity. The secondary lines are 

 very confused and almost obliterated by numerous scattered spicules. 



Sincules. — Smooth, slightly curved oxea (PL II. fig. 16), not very sharply but 

 rather gradually pointed; size about 0-37 by 0'021 mm. 



This species is distinguished by its beautiful and very characteristic external form 

 and by its hispid surface ; the spicules are rather large for the genus. 



Locality. — Royal Sound, Kerguelen, January 17, 1874 ; depth, 25 fathoms. Two 

 specimens. 



Genus Reniera, Nardo (Pis. I., II.). 



1847. Reniera, Nardo, Prospetto della fauna marina volgare del veneto estuario, Venice. 

 1864. Isodidya, pars, Bowerbank, Mon. Brit. Spong., vol. i. p. 197, &c. 



Skeleton composed of definite, rectangular (sometimes triangular or polygonal), 

 typically unispicular meshes. Spicules short oxea or strongyla, usually united together 

 at the ends only by spongin. 



' Perhaps due to a different mode of preservation. 



