REPORT ON THE MONAXONIDA. 73 



brittle, extremely sandy. Surface rougli and uneven, owing to the numerous foreign 

 bodies, Mollusc shells, Polyzoa, &c., with which the s^^onge is thickly encrusted. 

 Dermal membrane thin and transparent. Oscula scattered, small and round, with their 

 margins level with the general surface of the sponge, about 2 '5 mm. in diameter. 



Skeleton. — There is no dermal reticulation at all. The main skeleton is very loose. 

 The primary fibres are thin, and give off branches at very sharp angles, recalling the 

 ramification of the Broom. As they approach the surface of the sponge the primary 

 fibres break up into branches, each of which terminates in a sHghtly divergent tuft of 

 long, slender spicules which project little, if at all, beyond the dermal membrane. 



Spicules. — (a) Megasclera; of one kind only, viz., tylostyli (PI. XV. figs. 4, 4a), 

 long and very slender, each with a distinct head, and tajaering gradually to a fine 

 point at the apex; size about 0*4 by 0'0072 mm. (b) Microsclera ; (l) small, slender, 

 palmate anisochelse, about 0"028 mm. long ; (2) rather large, simple and contort sigmata, 

 measuring about 0"077 by 0'0048 mm. ; (3) trichodragmata, size about 0*35 by 0"07 mm. 



As already noticed, this sponge is very full of foreign bodies, and this renders it 

 difficult to obtain a satisfactory section. Indeed it seems as if the poor development of the 

 skeleton might be due to its partial replacement by foreign bodies. If we imagine the 

 process of degeneration proceeding a few steps further, we arrive at the condition of 

 Marshall's Phoriospongi^, the real nature of which has been discussed elsewhere. 



The small size of the chelae and the absence of a dermal skeleton are good 

 characters of this species. There can be little doubt that the modifications in the 

 skeleton are due to the sponge having lived on a shelly bottom. 



Locality.— Station 162, April 2, 1874; lat. 39° 10' 30" S., long. 146° 37' 0" E. ; 

 off East Moncoeur Island, Bass Strait ; depth, 38 fathoms ; bottom, sand and shells. One 

 large •specimen and some fragments. 



Usperella simonis, Ridley and Dendy (PI. XV. figs. 7, 7a, 12, 12a, 13, 16, 

 16a, 16?>, 16c). 



1886. Esperella simonis, Ridley and Dendy, Ann. and Mag. Nat Hist., ser. 5, vol. xviii. p. 339. 



Sponge branching, cylindrical (but rather angular), or more or less massive. 

 Diameter of branches about 8 mm.; length of largest fragment 45 mm. Texture 

 fibrous, elastic. Surface somewhat uneven and minutely hispid. Dermal membrane 

 thin, transparent, distinct. Oscula (?) small, scattered. Pores distinct, numerous, 

 round openings in the dermal membrane, about 0'063 mm. in diameter; irregularly 

 scattered, but very close to one another. 



Skeleton. — (a) Dermal; a rather irregular reticulation of spiculo-fibre, in some 

 places very much closer than in others, the extra closeness being due to numerous loose 

 spicules irregularly scattered between and across the fibres. In the looser parts, the 



(ZOOL. CHALL. EXP. — PART LIX. — 1887.) Nil 10 



