MR. A. DENDY ON WEST-INDIAN CHALININE SPONGES. 355 



The main skeleton (PI. LV1II. figs. 2, 2 a) is a network of stout, coarse, spiculo- 

 fibre, composed of very numerous, poly serially arranged, oxeote spicules, united together 

 by rather a small proportion of spongin, which is not sufficient, at any rate in most 

 cases, to form a distinct sheath around the fibre. One can readily distinguish with the 

 naked eye the primary fibres, running at right angles from surface to surface of the 

 tube-walls, and secondary fibres crossing them at right angles, and thus giving rise to a 

 more or less rectangularly meshed but rather irregular reticulation with wide meshes. 

 Towards the outer surface the reticulation becomes closer, owing to the interpolation 

 of new fibres, both primary and secondary, between the old ones. The average diameter 

 of the primary fibres is about - 06 millim., and of the secondaries somewhat less; both 

 contain a large quantity of imbedded foreign matter, such as grains of sand &c, lodged 

 amongst the spicules. The proper spicules of the sponge also occur fairly abundantly 

 scattered between the fibres as well as in them. 



In addition to the primary and secondary fibres thus described, one may trace, on the 

 inner surface of the tube-wall, a system of longitudinal fibres. 



The dermal skeleton, on the outer surface of the tubes, consists of a fairly close, 

 polygonally meshed reticulation of stout spiculo-fibre, containing a very large proportion 

 of spicules and but little spongin ; the average diameter of the fibres is about 0-03 

 millim. The ends of the primary fibres of the main skeleton form projecting nodes in 

 the dermal network. 



The spicules are slightly curved, sharp-pointed oxea, measuring about 0T38 by 0-006 

 millim. 



This species appears to be closely related to Esper's Siphonochalina (Spongia) tubu- 

 losa 1 , from the Cape of Good Hope; but we learn from Ehlers 2 that the spicules of 

 that species are twice as thick as here, and there would also appear to be no foreign 

 bodies in the fibre. The external form is also decidedly different in the two cases, as 

 will be seen by comparison with Esper's figure. 



Siphonochalina intermedia s , Eidley and Dendy, from Port Jackson, Australia, also 

 appears to be closely related, but differs considerably in the condition of the dermal 

 skeleton, in the slender fibre, containing much spongin, and in the absence of the 

 foreign bodies. 



Locality. Turk's Island, Bahamas. 



Siphonochalina pbocumbens, Carter, sp. (Plate LVlIT.fig. 4; Plate LXII. fig. 1.) 



1882. Paiuloscula procumbeus, Carter, Ann. & Mag. Nat. Hist. ser. 5, vol. ix. p. 365. 



This species has already been pretty fully described, but unfortunately not figured, 



1 Fortsetzungen der Pflanzenthiere, vol. i. p. 196, pi. liv. 

 1 Die Esper'schen Spongion, p. 19. 



3 Ann. & Mag. Nat. Hist. ser. 5, vol. sviii. p. 331, and Report on the Monaxonida collected by H.M.S. 

 ' Challenger,' p. 30, pi. vii. fig. 1 and pi. xlvi. fig. 3. 



