232 THE VOYAGE OF H.M.S. CHALLENGEK. 



dant occurrence of tlie familiar small ampliidiscs with hemispherical many-rayed terminal 

 discs (PI. XXXII. fig. 14). 



No hypogastral pentacts occur in the gastral skeleton, but their place is taken by 

 strands of supporting diacts. The autogastral pentact pinuli are essentially different from 

 the autodermal. They are not only decidedly shorter, and in no way so bushy as the 

 latter, but they exhibit longer, less tuberculated basal rays, and are continued into a 

 slender, pointed, terminal ray. 



The oxydiacts, which form the long marginal fringe, bear a smooth, proximal ray, 

 and a distal, beset with obliquely inserted spines, directed downwards and outwards. 

 From the centre two or more, rarely four, rounded, or slightly pointed, lateral tubercles 

 project. 



A much torn fragment with isolated, broken tuft spicules, was trawled to the west of 

 Cape York (Station 184, lat. 12° 8' S., long. 145° 10' E.), from a depth of 1400 fathoms, 

 and a Globigerina ooze ground. 



From the size of the shreds, and the thickness of the tuft spicules, it was to be 

 inferred that the intact body had the size of an average apple. There are no definite 

 indications as to the original form -of the body. 



In the parenchyma, besides long, narrow, smooth oxyhexacts and oxydiacts, small 

 lank oxyhexacts occur, some with straight, and others with bent, smooth rays, though 

 neither can be said to be abundant. 



The dermal skeleton exhibits large, smooth, hypodermal oxj^^entacts, with tangential 

 rays turned somewhat inwards, and long, slim, slightly spinose autodermal pentact pinuli 

 w^th moderately long, and terminally spinose basal rays (PL XXXIX. figs. 5, 7). Amphi- 

 discs of very various sizes and forms also occur. The larger exhibit a strongly developed 

 axial rod beset with spines, and bear rather broad, campanulate umbels, composed of 

 eight broad, paddle-like, terminally broad and rounded rays (PI. XXXIX. figs. 2, 3). 

 The length of these rays varies in relation to the total length of the amphidiscs, so that 

 they sometimes attain to only a third of the whole length, at other times to about a half, 

 and sometimes almost meet in the middle. The abundant medium-sized amphidiscs 

 (PI. XXXIX. figs. 4, 9) are slimmer, and bear narrower umbel rays in variable number. 

 Each umbel usually consists of eight rays, liut ten or twelve rays also occur. Finally, 

 as in all species of Hyalonema, small amphidiscs with hemispherical many-rayed 

 terminal umbels occur in great abundance. Some oxydiact marginalia were observed 

 with smooth proximal, and shortly toothed, pointed, distal rays, while on the boundary 

 between them, two or four rounded or slightly pointed tubercles projected (PI. XXXIX. 

 fig. 1). 



In the South Atlantic, to the west of Tristan da Cunha (Station 333, lat. 35° 36' S., 



