HYALONEMA (HYALONEMA) SP. 



221 



The basal acanthophores (Plate 68, figs. 27, 28, 31-33) have from two to 

 six rays, the tetractine (stauractine) forms greatly predominating. The tri- 

 to hexactines are 230-820 n long and have rays 11-33 m thick at the base. The 

 diactines are 0.7-1.15 mm. long and 7-30 ^ thick near the centre. Most of 

 them, particularly the shorter ones, are distinctly centrotyle; their central tyle 

 is 12-62 IX, which is sometimes 40 yu more than the adjacent parts of the spicule 

 in transverse diameter. The ends of the rays are thickened and densely cov- 

 ered with rather large spines. The remaining parts of the spicules are generally 

 smooth. In some stout-rayed tetractines a few spines arise also from the basal 

 parts of the rays (Plate 68, fig. 31), and some diactines have a very spiny central 

 tyle (Plate 68, fig. 27). 



In the lower part of the body fragments of uncinate anchor-spicules have 

 been observed. A spicule of this kind measured is 11 ^ thick just above the 

 anchor. The anchor is 25 n long and 18 fi broad. The anchor-teeth are rather 

 numerous, irregular, strongly recurved, and very blunt. 



The microhexactines (Plate 68, figs. 29, 30) are mostly rather regular and 

 measure 85-150 n in diameter. In some, two opposite rays are longer than the 

 other four. Such microhexactines are sometimes 200 n long and 120 /i broad. 

 The rays are 1.5-2.5 ti thick at the base, and usually slightly curved a little 

 beyond the middle of their length. This curvature is often unequal in different 

 rays of the same spicule. 



Occasionally monactine microhexactine-derivates have been observed. A 

 spicule of this kind measured appears as a tylostyle 120 fi in length and 1 fi 

 in thickness, with a terminal tyle 3.5 /x in diameter. 



Those amphidiscs (Plate 69, figs. 3-5) which can, with some degree of 

 probability, be assigned to the sponge, fall into five categories: — large and small 

 macramphidiscs, large and small mesamphidiscs, and micramphidiscs. 



The dimensions of these five kinds of amphidiscs are tabulated below: — 



