sPONctirDA. 613 



2 miUim. thick, which form the boundaries of cavities 1-2 millim. 

 wide, extending parallel to the surface ; the intervals between the 

 trabeculae are more or less tympanized by thin transparent mem- 

 branous expansions. Consistency in spirit — (a) of montioular specimen 

 soft and elastic, like Turkey sponge; (6) of subcylindrical specimens 

 tough, parchment-like. Colour — (a) almost white, (6) dull putty- to 

 reddish brown. 



Main skeleton — primary fibres approximately vertical to surface, 

 •05 to '07 millim. thick, -18 to -35 millim. apart; secondaries 

 approximately vertical to surface, but often curved ; size, as 

 primaries ; about "18 to '25 millim. apart. Dermal membrane in' 

 (a) based on fibre '035 to •! mUlim. thick, forming oval meshes •! to 

 •18 miUim. in diameter ; in (b) fibre '035 to ^088 millim^ thick, 

 meshes -14 to •S millim. wide, oval or oblong. Fibre brown of 

 various shades, axiaUy cored by one to four series of spicule no. 1, 

 eohinated abundantly by the spined acuate spicules. 



Spicules : — (1) Skeleton acuate, straight, tapering gradually from 

 near centre to sharp point on the one hand and to rounded base on 

 the other ; base about two thirds the diameter of centre, and carrying 

 a few very small spines ; size of spicule, "15 to •ITS by •0055 millim. 

 (2) Spiued acuate, straight, tapering gradually from base to sharp 

 point, base rather rugose ; spines sharp, small to moderate-sized, 

 those of proximal two thirds vertical to shaft, rather scanty, those 

 of apical third numerous, recurvate ; size of spicule ^075 by "0063 

 to -09 by •OOS millim. (3) Equianchorate, navicular, shaft almost 

 straight, slender; palms as seen from front truncate below, sub- 

 pyramidal, elongate (each more than one third the total length of 

 the spicule) ; tubercle rather elongate ; size of spicule, ^021 to -032 

 millim. (4) Same as (3), but shaft more curved, and size of spicule 

 only •Oil millim. 



Sab. Boudeuse and Etoile Islands, Amirante group, 10-13 fms. ; 

 bottom, sand or coral. 



The two externally very different forms which I have indicated 

 in the descriptionby (a) and (6) agree so closely in their microscopic 

 characters that I do not feel justified in separating them, even 

 varietaUy ; the absence of a tough cortex from (a) is perhaps due to 

 some local circumstance. 



The greatest vertical thickness of the largest specimen is 23 

 millim., the length 60 millim., the diameter of the lateral lobes 17 

 millim. The brown specimens have a strong external resemblance 

 to small specimens of the Hippospongice with meandrine canals, 

 and especially to H. derasa, mihi (see Part I., p. 382, of this Eeport) ; 

 also to fresh specimens of Ghalinopsis claihrodes, Schmidt ; and to 

 a specimen, now in the National collection, of an apparently MS. 

 species allied to Olathria, namei " Spongia multifora, Dufr.," but 

 which is quite distinct from C. deeumbens, owing to the strongly 

 spined skeleton-spicules. The very slender skeleton acuate with its 

 slightly spined head is an unusual feature in a OlatJiria, and few 

 Clathrias are without either a bihamate or tricurvate flesh-spicule. 

 The sessile massive habit distinguishes it from all other true 



