REPOET ON THE MONAXONIDA. 229 



which it inhabits ; (2) that the oscula are confined to one surface and the pores to the 

 other, exactly as in so many other sponges which have a lamellar form. 



The most closely allied species already known appears to be Cliona warreni. Carter,^ 

 but this is obviously distinct, as will be seen by comparison of the description {loc. cit.) 

 with ours. 



Locality. — Station 188, September 10, 1874 ; lat. 9° 59' S., long. 139° 42' E.; south 

 of New Guinea ; depth, 28 fathoms ; bottom, green mud. 



Family II. S p i R A s T r e l l T D .e, Ridley and Dendy. 

 1886. SpirastreUidee, Ridley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. p. 490. 

 Microsclera present ; typically forming a more or less continuous dermal crust. 



Genus Spirastrella, Schmidt (Pis. XLL, XLV.). 



1868. Spirastrella, Schmidt, Die Spongien d. Kliste v. Algier., p. 17. 



Sponge usually massive. Megasclera all monactinal, stylote or tylostylote. Micro- 

 sclera sjiined spirulse, occurring mainly as a dermal crust. 



Schmidt founded the genus for his species Spirastrella cunctatrix, and gives only 

 the following very brief generic diagnosis. " In der Eindenschicht eine eigenthlimliche 

 Art von strahligen Kieselkorperchen, deren Strahlen spiralig gestellt sind." A good 

 many species have been discovered since and the Challenger adds three new ones. 



Spirastrella decumbens, Ridley, var. (PI. XLV. figs. 12-12^'). 



1884. Spirastrella decumbens, Ridley, Zool. Coll. H.M.S. "Alert," Brit. Mus., p. 470, pi. xliii. 



fig. c. 



Represented in the collection by a single fine specimen, consisting of a number of 

 stout, irregular, anastomosing trabeculse, forming together a sessile, cavernous mass, 

 70 mm. long, by 44 mm. broad. The original tyjje was encrusting and thin, and of 

 small size, and must, therefore, be regarded as only a young specimen. There are also 

 slight difi'erenees in the proportions of the spicules between our specimen and the type, 

 the tylostyli (PI. XLV. fig. 12) and spined spirulse (PI. XLV. figs. 12a-12^) being 

 both of rather more robust growth in the Challenger specimen, the tylostyli measuring 

 0'4 by 0"015 mm., the spirulse 0'028 by 0*007 mm. (exclusive of the spines) ; but there 

 are no difi'erenees sufficient to justify us in separating the two specifically. 



1 Ann. and Mag. Nat. Hist, ser. 5, vol. vii. p. 370. 



