396 COLLECTIONS FROM MELANESIA. 



Main skeleton strictly rectangular; primary fibres *28 to -35 

 millim. apart at surface, secondaries *24 to *28 millim. ; primaries 

 ■053 to -| »7 millim. in diameter, spicules 2- or 3-serial; secondaries 

 •035 to '07 millim. in diameter, spicules uniserial ; horny matter 

 strong, pale amber-yellow, composing two thirds of the fibre 

 in the primary, and five sixths in the secondary fibres. Dermal 

 skeleton a strong, usually quadrangular network, tending to be 

 rectangular, of similar composition to the main skeleton ; between 

 its meshes is intercalated a close angular network of finer and 

 paler uniserially spiculate fibre, # 018 to "024 millim. in diameter, the 

 meshes -053 to "14 millim. in diameter. barcode pale umber- 

 brown, granular. Spicule slightly bent, smooth acerate, tapering 

 gradually to sharp points from three or four diameters from ends ; 

 size "115 by *007 millim. 



Hub. Alert and West Islands, Torres Straits, 7 fms. ; bottom 

 sand. 



Three good and some more or less fragmentary specimens in 

 spirit. The two largest are 120 and 115 millim. (44 and 4f- 

 inches) in length. The largest is composed of two stems, apparently 

 of independent origin, but one of them attached to and united with 

 the other at two points by broad masses of common substance. The 

 species is nearly allied to C. subarmigera, and hardly differs at all 

 exteriorly from the smooth form of that species except in its appa- 

 rently slight tendency to foi'm branches, but has the spicules of 

 about twice the diameter, and much fewer in number in proportion 

 to the horny matter, and the network of the main skeleton closer. 



It resembles Okalina montagui, Bowerbank ('? Fleming) (Great 

 Britain), in the general form and the size and shape of the spicules; 

 but the fibre in that species is less horny and stout, and has but one 

 or two series of spicules. 



It is a curious fact that at one of the points of union between the 

 two stems, as above described, a vent, originally belonging to one of 

 the stems, seems to have come into communication with the canal- 

 system of the other stem. 



Cladochalina nuda, var. abruptispicula. (Plate XLI. fig. j.) 



Repent?, with single series of vents on one surface about 2 millim. 

 in diameter, from 15 millim. and upwards apart, margins level 

 with surface. Stem 8 to 12 millim. in diameter, slightly compressed, 

 unbranched ; surface even. Colour, in dry state, brown. Texture 

 tough, elastic. Main skeleton rectangular. Fibre strong, pale 

 amber-yellow ; primary fibres about "088 millim. thick, spicules 

 axial, about 3-serial, -35 to '5 millim. apart, with a margin of 

 horny matter; secondary fibres, as primaries, but •044to , 088 millim. 

 thick, spicules somewhat loosely aggregated, 1- to 3-serial. Dermal 

 skeleton as in the typical form, but with stouter main fibres. 

 Sarcode pale yellow-brown, transparent. Spicules smooth acerate, 

 straight or almost so, coming abruptly to sharp points within 1! 

 diameter from ends ; size 107 by -0063 millim. 



