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



considerably in shape and size ; there are five kinds present ; (1) trichodragmata (PI. IX. 

 fig. 5, c); bundles of A^ery fine hairs, measuring (the bundles) about 0'455 by 0'175 mm. ; 

 these occur in great abundance ; (2) large, stout sigmata (PL IX. fig. 5, d), some only 

 very slightly contort, others considerably so ; size 0"06 by 0"0047 mm.; (3) small, thin, 

 contort sigmata^ (PI. IX. fig. 5, e), size 0-0189 by 0'0015 mm.; (4) a few tridentate 

 isochelas, about 0"019 mm. long ; (5) minute isochelse (PL IX. figs. 5,/, and 8), O'Ol mm. 

 long, of very peculiar form. The shaft is much expanded laterally and, when viewed from 

 the side, is seen to be notched in the centre. There is only one tooth at each end, which 

 is sharply recurved ; owing to the minute size it is difiicult to make out further details. 



Only one specimen of this species is present. It has evidently been cut from a 

 stone or some other attachment, so that in place of the base of the sponge a large 

 circular aperture is left ; this leads into a large cavity, caused by the shrinking up, and 

 perhaps partly by the loss of the internal soft tissues. Perhaps the most remarkable 

 feature about the sponge is the exceedingly hard and tough external rind, formed as 

 described above, a feature not at all common amongst the Desmacidonidge. The great 

 number and variety of microsclera is also noteworthy. 



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

 ofi" the south-west corner of New Guinea ; dej)th, 28 fathoms ; bottom, green mud. 

 One specimen. 



Genus lophon, Gray (Pis. XVI., XVII.). 



1867. Ioj3lion, Gray, Proc. Zool. Soc. LoncL, May 1867, p. 534. 

 1867. AleUon, Gray, Proc. Zool Soc. Lend., May 1867, p. 531.2 



Sponge soft and crumbling, usually dark coloured. Skeleton divisible into (a) a 

 dermal layer of diactinal spicules, usually tylota, i.e., with knobbed extremities which 

 may be smooth or spined, and (6) a deep-lying reticulation of loose spiculo-fibre, 

 composed of stylote spicules which are generally more or less spined. (? The proper 

 skeleton may be replaced by foreign bodies, such as sand-grains, foreign spicules, &c.) 

 Microsclera generally of two kinds. («) Palmate anisochelse, the small end of which 

 terminates in a sharp sj)ur ; these appear to be constant. (6) Bipocillate spicules, very 

 characteristic of the genus and almost always present, consisting of a curved shaft 

 terminated by a cup-shaped expansion at either end, which is sometimes divided into 

 lobes in a trefoil-like manner. 



Species of this genus may generally be recognised by the combination of several of 

 the above characters. A good external guide is the dark colour, many species being 

 black. The sponge is usually an amorpihous mass of crumbling substance, but it may 



^ Possibly young forms of tlie larger ones. 



2 For further generic synonyms, see under lophon patUrsoni. 



