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 n thick at the base. The 
diactines are 0.7-1.15 mm. long and 7-30 /x thick near the centre. Most of 
them, particularly the shorter ones, are distinctly centrotyle; their central tyle 
is 12-02 which is sometimes 40 n 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 n thick just above the 
anchor. The anchor is 25 /x long and 18 /x 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 ^ long and 120 n broad. 
The rays are 1.5-2. 5 m 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 
spicide of this kind measured appears as a tylostyle 120 /x in length and 1 n 
in thickness, with a terminal tyle 3.5 m 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: — 
Length of 
Breadth of 
Thickness of 
Diameter of 
Total length 
anchor 
anchor 
shaft 
central tyle 
V 
Large macramphidiscs 
2S0-316 
76-120 
90-104 
9-12 
1 3— IS 
Small macramphidiscs 
220-225 
77-80 
60-70 
8 
10 
Large mesamphidiscs 
136-168 
46-66 
22-43 
2-6 
2-8 
Small mesamphidiscs 
45-69 
23 
15-18 
1.5-2 
Micramphidiscs 
20-29 
4-7 
6-8 
0.6-1 
