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



Siphonochalina intermedia,^ Ridley and Deudy (PL VII. fig. 1 ; PI. XL VI. fig. 3). 



1886. Siphonochalina intermedia, Ridley and Dendy, Ann. and ]\Iag. Nat. Hist., ser. 5, 



vol. xviii. p. 331. 



Sponge (PI. VII. fig. 1) (sessile ? or stipitate ?), Lushily ramose. Branches stout, 

 tubular, sometimes anastomosing, short as compared with those of the next species, averag- 

 ing about 56 mm. in length and 16 mm. in diameter ; each branch varies considerably in 

 diameter in difierent parts of its length, and is broadest near the summit. All the 

 branches tend to grow vertically upwards. The total height of the single specimen in the 

 collection is 87 mm. and the breadth 116 mm., but something seems to have been cut off 

 from it. Colour in spirit greyish-yellow. Texture soft and spongy ; tough and fibrous. 

 Surface smooth, glabrous, with a reticulate appearance due to the underlying tissues 

 appearing through the delicate, transparent dermal membrane. Oscula, large circular 

 openings, one at the summit of each branch, about 8 mm. in diameter. 



Skeleton. — (a) Main ; the main skeleton, as seen in vertical section (PL XLVI. fig. 3) 

 is a very regular, rectangularly-meshed network of spiculo-fibre, the primary fibres run- 

 ning vertically to the surface, and the secondary ones crossing them at right angles. Both 

 primary and secondary fibres are rather slender, and have a core of polyserially arranged, 

 slender, oxeote spicules. The amount of horny matter in each fibre is large ; in the 

 primary fibres there are many more spicules than in the secondary ones. The fibres of 

 both sets measure about 0"032 mm. in diameter. There are also very numerous oxeote 

 spicules scattered through the choanosome between the fibres, (h) Dermal; the true 

 dermal skeleton is a very delicate, triangularly or polygonally-meshed reticulation of 

 spiculo-fibre, the fibre forming each side of a mesh being composed of a single spicule and 

 a very large proportion of horny matter. (When mounted in Canada balsam the horny 

 fibre is rendered almost invisible, and the dermal skeleton then appears as a unispicular 

 reticulation of oxeote spicules.) The dermal skeleton is supported on the ends of the 

 primary fibres, which also form the nodes in a much coarser reticulation of stouter 

 spiculo-fibre lying immediately below it. 



Spicules. — Slender oxea, rather abruptly piointed, measuring up to about O'l mm. in 

 length, and up to about 0"006 mm. in thickness, but usually slenderer. 



This sj)onge certainly comes very close to Esper's Spongia tiibulosa,^ but the spicules 

 in that species are, according to Ehlers,^ twice as thick as in ours. Possibly Siphono- 

 chalina intermedia should be regarded as only a variety of Spongia tiohulosa, Imi until 

 more is known of the skeleton arrangement in the latter species the two had better remain 

 distinct ; as regards external form, they are almost identical {vide Esper's figure, loc. cit.). 



Locality. — Port Jackson ; 7 to 8 fathoms. One specimen. 



' This species and the next were also obtained by Dr. v. Lendenfeld, who first used the specific names inter- 

 Ttiedia and annulata in his MS. Catalogue. 



* Fortsetz. der Pfianzenthiere, pt. i. p. 196, pi. liv. ^ Die Esper'schen Spongien, p. 19. 



