Mr. H. J. Carter on the Hexactinellidee. 367 



end of a conical sac, is enveloped in a bunch of white horse- 

 hair-like, long, anchoring-spicules, respectively smooth and 

 spiniferous, with hooks at the free extremity of the latter. 



2nd. Euplectella cucumer has the spicular basketwork of 

 the lid alone cemented together by an envelope of vitreous 

 ladder-like fibre, while all the spicules of the basketwork 

 of the body below are cemented together by sarcode only. The 

 main lines of spicules &c. are the same as in E. aspergillum ; 

 but there are no ridges or frills, their place being supplied by 

 robust vertical spines one eighth of an inch long, respectively 

 situated in the centre of each square of the matted basketwork, 

 so that the spiral lines of holes are between rows of spines, 

 which thus replace the ridges in E. aspergillum (PI. XIV. 

 fig. 10, a a a). Indeed there is a special form of sexradiate 

 spicule produced for this purpose, in which the projecting spine 

 or ray is far more robust than any of the rest, the opposite 

 continuation or internal arm being more or less aborted, and 

 the four horizontal ones extended diagonally along the squares 

 of basketwork to meet the corresponding arms of their neigh- 

 bours. This spicule is delineated in the original description of 

 the sponge by Prof. Owen (Trans. Linn. Soc. 1857, vol. xxii. 

 pi. xxi. fig. 5), and its position pointed out in the explanation of 

 the plate, but does not appear in the figure of the sponge itself. 

 In other respects E. cucumer is generally like E. aspergillum, 

 but possesses a number of minor differences, which it is not 

 requisite to mention now. 



3rd. Alcyoncellum speciosum and^l. corbicula {Habrodictyon, 

 Wy. Thomson) have no vitrified fibre in their composition. 

 The spicules of which their basket-like structure is composed are 

 stated by Prof. Thomson, who examined the specimens, to 

 be cemented together by a " small quantity of mucilaginous 

 sarcode " only ('Annals,' 1868, vol. i. p. 126) ; and it is evident 

 from the photograph that the main spicules present no regularity 

 in their arrangement like those of Euplectella aspergillum and 

 E. cucumer — that is, that they do not for the most part cross 

 each other at right angles, in consequence of which neither the 

 holes nor the interspaces are regular either in size or direction, 

 while the interspaces present neither " ridges" nor "spines." 

 Neither does either of these specimens possess any anchoring- 

 spicules; while, as evidence of their sessile growth, Alcyoncellum 

 speciosum still retains at its base a portion of the rock to which 

 it was attached. On this difference, however, I do not wish 

 to lay any particular stress, because I have a specimen of 

 Euplectella aspergillum (fragment of the base) in the same 

 condition — that is, sessile, on a fragment of Lophokelia pro- 

 lifera dredged up on board H.M.S. 'Porcupine' on this side 



25* 



