REPORT ON THE MONAXONIDA. 21 



subglabrous, with a faintly reticulate appearance, due to the subdermal cavities showing 

 through the dermal membrane. Dermal membrane distinct, thin, transparent, 

 perforated by numerous scattered pores. Oscula rather small and shallow ; chiefly on 

 one side of each branch ; diameter little over 2 mm. 



Skeleton. — («) Dermal; a close, small -meshed reticulation of rather loose spiculo-fibre, 

 echinated at the nodes by small bundles of outwardly projecting spicules, which are, at 

 any rate in part, the projecting ends of the primary filjres. (h) Main; a rather irregular 

 reticulation of spiculo-fibre and scattered spicules, in which primary and secondary 

 fibres are distinguishable but not very well marked. Fibre much slenderer than in 

 Pachychalina fragilis, but still without a very evident external sheath of spongin as 

 in typical Chaliniaae. 



Spicules. — Eather slender, slightly curved, gradually and usually sharply pointed 

 oxea; size about 0"175 by 0"0126 mm. 



This species, though very distinct from both, forms a connecting link between 

 Pachychalina fragilis and Pachychalina^ Jihrosa, which is next described, and which 

 has much slenderer spicules, and a greater amount of spongin in the fibre. 



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

 Philijjpine Islands ; depth, 18 fathoms ; bottom, blue mud. Two specimens. 



Pachychalina Jihrosa,, Ridley and Dendy (PL IV. figs. 3, 4). 



1886. Dasyclialina fibrosa, Ridley and Dendy, Ann. and Mag. Nat. Hist, ser. 5, vol. xviii. 



p. 330. 



Sponge (PL IV. fig. 3) erect or rej)ent ; branched. Branches stout, irregular, 

 coarsely aculeated ; bearing large circular oscula, usually on one side only. Diameter of 

 branches ranging from about 6 to 25 mm. Length of spines varying greatly in different 

 specimens, up to about 4 mm. Colour in spirit greyish-yeUow. Texture coarsely 

 fibrous, compressible and elastic. Surface coarsely aculeated, reticulate. Dermal 

 membrccne distinct, thin, translucent. Oscula large, cii'cular, shallow (i.e., the exhalent 

 canals terminate at the bottoms of shallow depressions, vide figs. 3, 4). 



Skeleton. — (a) Dermal; a very coarse reticulation of stout spiculo-fibre with usually 

 triangular meshes, broken up by a much finer and rather irregular reticulation of very 

 slender spiculo-fibre. The coarse fibre contains a very great number of spicules, and 

 comparatively little spongin ; measuring about O'l mm. in total thickness. Tlie finer 

 fibre is very slender, contains a larger proportion of spongin, and usually only a single 

 row of spicules; thickness about O'OIS mm. (&) Main; a reticulation of very stout, 

 branching and anastomosing spiculo-fibre; measuring up to about 0*14 mm. thick, and 

 almost or quite filled with densely packed spicules. Spicules occur also very abundantly 

 outside the fibre ; irregularly scattered through the choanosome. 



