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



measures only 2 cm. In other respects the form and structure are not essentially 

 diflerent. The somewhat lirighter colour is rather striking, being in these three forms light 

 greenish-yellow, while those from Station 246 were dark dull greenish-brown. The 

 section in PI. XXXVI. fig. 1, is a diagrammatic representation of a longitudinal section 

 through the external marginal portion of one of the specimens from Station 271. 



4. Hyalonema {Stijlocalyx) davigerum, n. sp. (PI. XLL). 



In the neighbourhood of the Penguin Islands (Station 147, lat. 46° 16' S., long. 48° 27' 

 E.), from a depth of 1600 fathoms, and from a Diatom ooze ground, a fragment of a 

 Hyalonema was dredged, which is represented in PI. XLI. fig. 1. The fragment represents 

 about one-eighth of the whole body, and is without any trace of the basal tuft, but still 

 exhibits a portion of the oscular margin and one of the radial septa. The consistence of 

 this sponge fragment, which is about 5 cm. long, and represents a probably truncated 

 oval body, is not so great as that of Hyalonema globus. The whole external surface 

 distinctly exhibits a well-developed rectangular dermal framework. 



The parenchymal skeleton consists again of somewhat large smooth and radially dis- 

 posed oxyhexacts, and of simple oxydiacts which are either smooth, or have a median 

 swelling or four projecting median knobs. Between these, thin forms equipped at both 

 ends with delicate barbs (PL XLI. fig. 6) occasionally occur, like those found abundantly 

 in the parenchyma of Hyalonema globus (PI. XL. fig. 5). 



Besides these, minute delicate oxyhexacts occur in some abundance, exhibiting fine 

 straight pointed rays, on which a gentle curvature may, here and there, be detected 

 (PI. XLI. fig. 7). 



Those oxyhexasters which are represented in large numbers in the diagrammatic 

 section of PI. XLI. fig. 2, and under high power in PI. XLI. fig. 5, do not really belong 

 to this sponge, nor indeed to the genus Hyalonema, but are forms which have been 

 accidentally imported. 



The dermal skeleton is mainly composed of somewhat large smooth hypodermal 

 oxypentacts, with oblique, inwardly directed tangential rays. On the outer surface 

 numerous autodermal pentact piuuli occur, with rather long, smooth and pointed, basal 

 tangential rays, while the relatively short distal ray bears, as in Hyalonema globus, 

 long, fine, upwardly bent lateral spines, and a knob-like external terminal portion with 

 thick, somewhat pointed axial end, and so has a tufted appearance (PI. XLI. fig. 4). 



The somewhat large amphidiscs which are irregularly scattered in radial disjaosition 

 within the external skin, exhibit a firm smooth axial rod with several (four or eight) 

 radially projecting tubercles in the centre. The bell-shaped terminal umbels are rather 

 broad, and measure about one-fourth of the total length. They consist of eight broad 

 shovel-shaped rays with lancet-like pointed ends (PL XLI. fig. 9). There is a much sparser 



