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



terminal rays are, fiirtlier, for the most part somewhat wavy in their curvature (Ph LIX. 

 figs. 8, 9). I did not discover any small discohexasters. 



The dermal and gastral skeletal elements correspond almost perfectly to those of 

 Bathydorus stellatus, though it may be noted that the gastral oxyhexacts are here very 

 varied, sometimes rough, sometimes spinous, and rarely quite smooth, as represented in 

 PI. LIX. fio-. 7. In general, in spite of the larger size of the specimen, the rays of its 

 hexact gastralia are less strongly developed than in the much smaller specimens of 

 Bathydorus stellatua. 



The pleural and marginal prostalia are, like those of Bathydorus stellatus, simple 

 smooth oxydiacts, 8 to 10 mm. iu length. 



4. Bathydoms haculifer, n. sp. (PI. LIX. figs. 10-18). 



In the middle of the South Pacific (Station 286, lat. 33° 29' S., long. 133° 22' W.), from 

 a depth of 2335 fathoms and a red clay ground, the trawl brought up a small fragment 

 of a sponge which apparently belongs to the genus Bathydorus. The specimen, as 

 figured in PI. LIX. fig. 10, is a tolerably smooth, approximately semicircular plate, 

 2 mm. in thickness. From the smooth surface some isolated simple oxydiacts project 

 obliquely for 10 to 20 mm., while the other surface appears uniformly rough. 



The spicules of the parenchyma are long, narrow, smooth diacts, with rough, conically 

 pointed, rounded, or more rarely slightly club-shaped ends, with or without central nodes, 

 exactly as in the other species of Bathydorus. Medium-sized simple hexacts occur here 

 and there. Between these there is a very abundant occurrence of oxyhexasters with 

 short principal rays and long straight terminals (PI. LIX. figs. 12, 13). A few disco- 

 hexasters also occur with short principal rays, each of which bears usually three diverging 

 terminals, bent convexly outwards at their base, and carrying on their extremities 

 minute, transverse, four-toothed, somewhat convex discs (PI. LIX. fig. 18). 



The dermal skeleton contains medium-sized hypodermal pentacts, with rough, 

 rounded, or somewhat conical extremities, and small autodermal diacts or monacts, 

 which are rough all over, are rounded ofi" at their ends, and exhibit at the central point 

 a definite swelling of the axial canal, or the trace of undeveloped rays, usually in the 

 form of two opposite, or more rarely four cruciate tubercles (PI. LIX. figs. 14, 15, 16, 17). 

 The hypodermal pentacts form, by the apposition of their opposite tangentials, a quadrate 

 lattice-work. The autodermal diacts and monacts occur in irregular disposition in the 

 dermal membrane (PI. LIX. fig. 11). In the diacts the two rays belong as a rule to the 

 same axis, but forms occasionally occur, as figured in PL LIX. fig. 16, where the two 

 rays form a right angle. In the monacts, which occur in tolerable abundance, the end 

 which represents the centre of the original six-rayed form, and which therefore contains 

 the node of intersection of the axial canals, exhibits a club-shaped thickening, and it may 



