SPONGES. 70 



(3.) Spherasters (Plate II ., fig. 7, /, y) ; with well -developed centrum and sharp, 

 conical rays ; total diameter about - 024 millim., with rays about O'OOS milliui. long ; 

 most numerous in the dermal crust, but also abundant below. (A rather noteworthy 

 feature of these spicules, in many cases, in the boiled-out preparations, is the 

 conspicuous nature of the central canal in the rays, which gives the spicule a very 

 peculiar appearance.) 



(4.) Oxyasters (Plate II., fig. 7, h, i) ; with very small centrum and a rather small 

 number of slender, finely-pointed, smooth rays ; total diameter up to about 0*024 

 millim. Abundant in the choanosome. 



This species is particularly interesting on account of the extreme reduction of the 

 cladi of the trisenes, affording an absolute transition from the tetractinellid to the 

 monaxonellid condition. This vestigial condition of the cladi, an approach to which is 

 already seen in Stelletta herdmani, appears to be associated in this genus with the 

 irregularly scattered arrangement of the trisenes (compare the vestigial condition ot 

 the cladi of the dermal anatriaenes in Geodia peruncinata, described later on). 



1I.N. 200A (Station LXVIL, off Talaivillu Paar, 10-14 fathoms). 



Ecionema, BOWERBANK. 



The microscleres include microrhabds in addition to euasters ; the former are commonly 

 minutely spined or roughened, and usually form a dermal layer. 







Ecionema carter!, n. sp. Plate I., fig. 5 ; Plate III., fig. 1. 



There are three specimens of this sponge in the collection. The largest and only 

 well-developed example (II. N. 175, Plate L, fig. 5) may be taken as the type of the 

 species. This specimen is massive and quite irregular in shape, with a number of 

 foreign bodies attached to it. The maximum diameter is about 35 millims. The 

 surface appears, in most places, distinctly porous, even to the naked eye, owing to the 

 presence of very numerous, thickly scattered, small pore-sieves (Plate L, fig. 5, jJ.s.) 

 containing the inhalant pores. It is also very minutely and sparsely hispid, at any 

 rate in parts. The vents (Plate I., fig. 5, o) are rather numerous, without prominent 

 margins ; circular or oval openings varying up to about 2 millims. in diameter ; 

 mostly congregated in a depression on what was apparently the upper part of the 

 sponge. They are the apertures of wide, diaphragm-bearing oscular tubes. The 

 texture of the sponge is fairly firm, but compressible. The colour in spirit is pale 

 grey. 



Another specimen (li.N. 188) is almost spherical and only about 11 millims. in 

 diameter, without visible vents ; it is probably immature. The third (R.N. 259) is 

 an irregular fragment. 



The main skeleton in the interior of the sponge is an irregular interlacement of 

 large oxea which, towards the surface, collect into loose radiating wisps, ending in 



