614 



COLLECTIONS FROM THE WESTERN INDIAN OCEAN. 



Clathrias, except perhaps C. elegans, Vosmaer (habit unknown), and 

 G. {Diclyoayliridras) a ncJiorata, Carter. The latter is on ly known 

 from small shapeless masses, and has the skeleton-spicule stout, 

 smooth, and strongly curved: otherwise the spicular complement 

 is essentially the same. In the present species the two kinds of 

 anchorates appear to be distinct, the smaller form being very 

 abundant, the larger, though evidently normally present, much less 

 common ; the occurrence ' of a larger and smaller anchorate in some 

 Esperice, as pointed out by Carter (Ann. & Mag. N. H. 1882, ix. 

 pp. 298, 299), is an analogous circumstance. 



36. Clathxia maeandrina. (Plate LIII. fig. I ; Plate LIV. 



figs, h-h".) 



Sponge only known as an incrusting, widely-spreading mass, 

 consisting of a thin basal lamina not exceeding 1 millim. in thickness, 

 from which arise vertically, at intervals of 1 to 3 millim., parallel- walled 

 ridges, or triangular masses, about -5 to 1*5 millim. in diameter and 

 2-4 millim. in height, usually united laterally to form a series of 

 meandrine ridges, generally 2-3 millim. apart, at the surface of the 

 sponge. Surface of basal lamina very uneven under lens, honey- 

 combed with round openings *25 to -75 millim. in diameter; the 

 trabecula between the openings is hirsute with projecting spicules ; 

 surface of vertical ridges uneven, densely hirsute with projecting 

 spicules and skeleton-fibres, towards the base it has a honeycombed 

 appearance similar to that of the basal lamina. Consistence in spirit 

 slightly resistent, but soft, compressible, elastic. Colour in spirit 

 buff-yellow. 



Main skeleton — arrangement subrectangular ; fibre dense, pale 

 amber-yellow, echinated sparsely below surface of sponge by spicule 

 no. 2, set at right angles to fibre. Primary fibres approximately verti- 

 cal to surface, terminating on it in short horny points densely clothed 

 with spicule no. 1, which are directed outwards, parallel to the axis 

 of the fibre : diameter of fibre about -05 to *1 millim. ; cored with 

 proper spicules, usually biserially arranged, to a variable distance, 

 not exceeding - 7 millim., below surface; distance of fibres apart 

 about -17 to -35 millim. Secondary fibres uncored, -035--07 millim. 

 thick, placed at intervals of about -17 millim., approximately vertical 

 to primaries. Dermal skeleton composed of a rather close rect- 

 angularly-meshed reticulation ; fibres about "04--07 millim. thick, 

 apparently covered in parts by a thick incrustation of foreign 

 bodies. Sarcode transparent, very palo yellow-brown. 



Spicules : — (1) Acuate, or with slightly constricted base, either 

 smooth or with the base minutely spined, moderately curved, tapering 

 gradually from base to sharp point ; size -023 by 'Ol 1 to -013 millim. 

 (echinating the apices of primary fibres). (2) Spined acuate, straight; 

 a head slightly indicated by a subterminal neck, spines minute to 

 moderate-sized, placed at right angles to long axis : size of spicule 

 •I 175 by •<)! >63 millim. (echinating fibres of main skeleton). (3) Sub- 

 spiuulateor acuate, smooth, almost straight, tapering gradually from 



