230 THE VOYAGE OF H.M.S. CHALLENGER. 



Zoca%.— Station 208, January 17, 1875; lat. 11° 37' N., long. 123° 31' E. 

 Philippine Islands; depth, 18 fathoms; bottom, blue mud. One specimen. 

 Habitat. — Torres Strait (Ridley, "Alert"); Philipjiine Islands (Challenger). 



Spirastrella massa, Ridley and Dendy (PL XLV. figs. 14-14^). 



1886. Spirastrella massa, Kidley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. p. 490. 



Sponge massive, represented in the collection by two large, squarish blocks, which 

 have evidently been cut out of a very large specimen, or possibly from tw^o. Coloui- 

 in spirit pale, greyish-yellow. Texture fairly compact throughout, but rather spongy. 

 Surface almost glabrous in appearance, but rather lumpy and uneven ; very mini;tely 

 hispid. Dermal memhrane thin, transparent. Oscula ; one or two scattered ones, of 

 moderate size, have been observed, hut it is very probable that many more were present 

 in the entire specimen ; possibly they were mainly locahsed in some portion of the sponge 

 which has not been preserved. Pores, small round openings, thickly scattered in some 

 parts, so as almost to reduce the dermal membrane to a network, very rare or almost 

 undisceruible in other parts ; diameter, taken from a part of the sponge where they were 

 abundant, about 0"06 mm. 



Skeleton. — Very difiuse and with no distinct spiculo-fibre ; consisting of abundant, 

 irregularly scattered stylote and subtylostylote spicules. Immediately beneath the 

 surface these spicules are much more closely packed than elsewhere and are also, for 

 the most part, horizontally disposed. They thus form a fairly thick cortical layer, not, 

 however, very well defined from the deeper skeleton. At the surface itself are irregular 

 tufts of stylote spicules whose apices project for a short distance beyond the dermal 

 membrane. 



Spicules. — (a) Meyasclera ; slightly curved, rather slender, smooth styli or subtylo- 

 styli (PI. XLV. figs. 14, 14a, 146); the heads, when present, are somewhat irregularly 

 developed ; apex not very constant in form, sometimes very sharply and gradually 

 pointed, at others more blunt, sometimes slightly and irregularly jagged; size about 

 0"45 by 0'0065 mm.; in the surface brushes a trifle shorter, (b) Microsclera; smaU 

 spined spirulaj (PI. XLV. figs. 14c-14^), the largest of which are slender, have five or 

 six bends, and measure about 0"044 mm. in length. These are, however, not nearly 

 so numerous as the smaller ones, which often consist of only one short length with 

 spined ends; about 0'0095 mm. long. As forms intermediate between the two described 

 can be found, it seems probable that they are all merely different stages of the same 

 spicule. These spicules are nowhere abundant except in the dermal membrane, where 

 they are very plentiful. 



Perhaps the two most remarkable characteristics of this species are its singularly 



