72 



The tubular main skeleton-net lies nearer to the inner, than to the outer 

 surface of the tube- wall, the greater part of the parenchyme and of the folded 

 chamber-layer being situated outside of it. This parenchyme is supported 

 by the radial rays of the hypodermalia and hypogastralia and by one or 

 two layers of pretty numerous parenchymal oxyhexactines, two opposite rays of 

 which are vertical to the surface. The rays of these spicules are 100-150 /^ 

 long, about 4 i^ thick, always quite straight and either smooth or covered with 

 sparse, pretty long and slightly curved, vertical spines (pi. XII. f. 2). 



The parenchymal hexasters are exceedingly numerous throughout the soft 

 parts ; there is a very unusually large number of different he'xaster-forms in 

 this species. The most numerous hexasters are in both specimens discohexasters 

 of varying size. Bach of their main-rays bears a considerable number, mostly 

 five, seven, or nine, long branch-rays which are distally thickened, club-shaped 

 and which end in transverse, circular, convex terminal discs, the sharp margins 

 of which have six to eight slightly recurved teeth (pi. XII, f. 8-12). All the 

 branch-rays of these discohexasters are nearly equidistant and so arranged that 

 their terminal discs lie in the surface of a sphere, the centre of which coincides 

 with the centre of the spicule. Most of these discohexasters measure 200 i^ in 

 diameter; middlesized ones, 160 /^ in diameter; and numerous smaller ones only 

 100 A^ , or even 80 F- in diameter, are also met with. 



In another kind of hexaster with similar, circular, transverse, sharp-mar- 

 gined, terminal, toothed discs the disc-teeth are 6-8 in number, exceedingly long 

 and slender and so strongly recurved as to extend backwards, parallel to the 

 branch-ray to which they belong. Together with the terminal disc itself, the 

 marginal teeth form in these hexasters a deep bell (pi. XII, f. 13-15). In con- 

 sequence of this remarkable shape of the branch-ray-terminations I have desig- 

 nated these spicules as codonhexasters. They are in both specimens pretty numer- 

 ous. Two varieties of codonhexasters can be distinguished, differing by their size, 

 their shape and the number of their branch-rays. The codonhexasters of the large 

 variety measure 60-80 M in total diameter and have a small central thickening 

 from which the six slender main-rays arise. These are 6 /* long and each one 

 bears five to seven, straight and very slender branch-rays, 24-30 /* long. The 

 latter are distally extended to form terminal, bell-shaped structures which con- 

 sist of a small, central, convex, transverse terminal disc with six to eight recurv- 

 ed, slender rod-like marginal teeth, extending backwards, parallel to the branch- 

 ray to which they belong. These rod-bells are about 8 i^ long and 4 m broad 

 (pi. XII, f. 14-15). All the terminal bells lie in the surface of a sphere so that 

 the whole spicule is spherical in shape (pi. XII, f. 13). 



The smaller variety of codonhexasters is only 40 m in diameter, has a somewhat 

 different shape and is, in consequence of the extreme minuteness of its parts, 

 rather diificult to see. The main.rays are 8 /* long and bear a much greater 



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