184 Mr. S. 0. Ridley on Sponges. 



planes ; branches tortuous, more or less compressed, sometimes 

 forming broad expansions terminated by subcylindrical pro- 

 longations, simple or branched ; greatest diameter of terminal 

 branches about 10 millim. Surface either approximately 

 even, or echinated by few and sharp vertical projections, 1-2 

 millim. high. Vents numerous, opening flush with surface, 

 and entered at a slight depth by the openings of the excre- 

 tory canals ; diameter 1-1 '5 millim., scattered at intervals 

 of 3-7 millim. over the anterior surface of the branches. 

 Consistency in spirit firm, but compressible and elastic ; in 

 dry state firm, but harsh to touch, and but slightly compressi- 

 ble and elastic : colou]' in spirit bright ochreous brown, in dry 

 state pale grey. Main skeleton approximately rectangular 

 in arrangement ; primary fibres about *4 millim. apart at 

 surface, where they terminate vertically in the dermal reticu- 

 lation, diameter about '1 to "14 millim.; secondary fibres 

 vertical to primaries, about '3 millim. apart, diameter '07 to 

 •1 millim. ; fibres of both kinds consisting of a compact axial 

 mass of spicules, and of a margin of transparent pale amber- 

 yellow horny substance about '025 millim. broad. Dermal 

 skeleton forming subquadrate meshes "18 to "SG millim. in 

 diameter, formed of spiculo-fibres, which are usually devoid of 

 any visible horny margin, and range in thickness from *025 

 to "1 millim. Sarcode pale amber-yellow, subtransparent. 

 Spicules smooth acerate, slightly curved, tapering to sharp 

 points from within about two diameters of ends, size '11 by 

 •0063 millim. 



Hah. Singapore, between tide-marks. 



This species was obtained by H.M.S. ' Alert,' and figured 

 in the 'Report ' &c. [I. c. supra), but not described. 



The largest specimen, which is dry, is very irregularly 

 rooted, and near its base shows the palmate development of 

 the stem and branches very strongly ; it measures 190 millim. 

 (7| inches) greatest lateral, and 95 millim. (3| inches) in greatest 

 present height ; its branches are almost smooth, but those of the 

 younger spirit-specimen show the aculeation above described. 

 Both specimens deviate from the erect habit in the turning of 

 the branches outwards and to the sides soon after they are 

 given ofi". 



The fibre is stronger and stouter than in any Cladochalina 

 with which I am acquainted, and gives the species the firmness 

 of a Pacliychalina ; in the tendency to become flattened it also 

 resembles that genus. 



The variation in the character of surface aculeation exhi- 

 bited by this Chalinid is important and significant in relation 

 to its value in classification. 



