SPONGES. 181 



The surface is uneven but fairly smooth ; granular ; with a distinct, translucent 

 dermal membrane in places. Vents probably small and scattered. Texture rather 

 soft, spongy and friable. Colour (in spirit) dull grey. Greatest diameter of the entire 

 mass about 48 millims. 



The skeleton is a close-meshed, very irregular reticulation of megascleres, many ot 

 which are collected together into loose nmlti-spicular bands running perpendicularly 

 to the surface. These primary fibres, if we may so call them, are connected together 

 by still looser and more irregular secondary bands, and the whole is confused by 

 immense numbers of irregularly scattered megascleres. There is no special dermal 

 skeleton and I have detected no spongin. 



Spicules. (1.) Styli, " rhabdostyles" of Topsent (Plate XII., fig. 10, a, b, c) ; base 

 evenly rounded off, not tylote ; basal part of shaft sharply bent at an angle to the 

 remainder, like the end of a hockey stick, occasionally somewhat spirally curved ; 

 remainder of shaft straight or nearly so ; gradually or somewhat hastately pointed at 

 the apex ; size fairly uniform, about 0"24 millim. by 0'006 millim., the bent basal 

 portion being about 0"018 millim. long. These make up the main skeleton. 



(2.) Very small, slender styli (Plate XII., fig. 10, d) ; straight or nearly so; 

 tapering gradually from rounded base to finely pointed apex ; with very slightly 

 roughened surface; size about 0"044 millim. by - 002 millim. at the base. Scattered 

 very abundantly through the soft tissues as microscleres, and very uniform in size. I 

 am inclined to think that these spicules are vestigial echinating styli. 



(3.) Sigmata (Plate XII., fig. 10, e) ; very much contort, slender, often twisted 

 into a kind of half-knot in the middle, sharply pointed at each end (when one end 

 appears bluntly rounded, or even knobbed, it is probably due either to its having been 

 broken short or to fore-shortening in perspective). The greatest length, measured in 

 a straight line from bend to bend, is only about 0'012 millim., but if the spicule were 

 straightened out it would measure at least twice as much. Very abundant. 



This species is distinguished from Rhabderemia pusilla by the greater length of the 

 bent styli and the much smaller size and roughened surface of the minute styli; 

 from R. guernei by the absence of the peculiar microscleres which Topsent terms 

 " thraustoxes," and by the smaller size of the megascleres and the roughening of the 

 minute styli ; from R. intexta by the presence of the minute styli, the smoothness of 

 the large megascleres and the form of the sigmata. It differs from all in its much 

 more robust growth, which constitutes perhaps its most noteworthy feature. 



R.N. 341 (Ceylon seas). 



Family: AXINELLID^E. 



Sigmatomonaxonellida in which the microscleres have usually been entirely lost by 

 degeneration; the megascleres are usually, in part or entirely, stylote ; the 

 skeleton arrangement is usually, but not always, plumose ; and there are no 

 spined echinating styli. 



