380 ~ Mr. T. Higgin on a new Hexactinellid 
spines bent, and all pointing towards one and the same end of 
the spicule; 5, fusiform-acerate, sparsely spined throughout, 
but the spines on each half pointing respectively towards the 
middle ot the spicule (Pl. XXI. fig. 3) ; 6, the largé stout, 
smooth acerate (whose measurements have just been stated), 
conspicuous from its great size amongst the other forms with 
which it 1s associated (Pl. XXII. fig. 1); 7, slender, smooth, 
crucial or four-armed spicules, the arms horizontal and at 
right angles to each other; 8, similar-shaped spicules, larger 
than the last named, but barbed harpoon-like towards the 
ends of the arms (Pl. X_XI. fig. 4) ; 9, small sexradiate forms 
furnished with rather long spines, which commence about half- 
way along the rays, shooting out in the direction of their 
points and bent upon themselves outwards (fig. 5); 10, a nail- 
like form with short straight arms and long plumose shaft, spines 
rather short; 11, large eight-armed birotulates, about 1-90th 
of an inch in length, with dome-shaped heads and four or eight 
tubercles, chiefly confined to a ring round the middle of the 
shaft; 12, a small eight-armed birotulate of slender form, 
about 1-225th of an inch in length (fig. 6), the shaft of 
which is studded throughout with short obtusely pointed 
spines, the heads not dome-shaped but pointed; 13, a very 
minute birotulate, averaging 1-1250th of an inch in length, 
having the appearance of bearing only two arms at each end 
(fig. 7), but, when carefully focused endwise, is seen to be 
multihamate, the normal number of its arms being probably 
eight, though in some instances six only can be counted, whilst 
in others ten may be seen, the shaft spined more or less 
throughout, and the heads dome-shaped; this minute spicule 
is found in great numbers in the dermal sarcode, as well as 
generally throughout the sponge. 
The long fusiform-acerate spicules form the fibrous lines of 
the general structure, on which are seen the large birotulates 
and the long-shafted plumose forms ; whilst the crucial spicules 
are found in the sarcode of the walls of the canals. Most of 
the acerate forms are of the sexradiate type, as is evident from 
the cross in the central canal in the middle of the spicule ; but 
the main shaft only is produced, the arms either not being 
produced at all or appearing only as tubercles. 
The spicules of the sponge immediately embracing or sur- 
rounding the glass rope where it issues from the mass are 
several varieties or modifications of the sexradiate type. ‘There 
is no Polype on the rope, nor any membranous covering of any 
kind. The sponge-head is grooved inwards circularly round 
the rope, as a pear often is round the stalk ; and the plumose 
spicules of the dermal latticework can be traced close up to the 
