254 HYALONEMA (PRION EM A) AGUJANUM. 
Distal ray 
Lateral rays 
length 
n 
basal thickness 
n 
maximum thick- 
ness, together 
with the spines 
M 
length 
n 
var. tenuis 
form A 
120-160 
3-6 
4-10 
70-98 
form B 
225-280 
6-7 
18-20 
60-80 
var. lata 
176-280 
5-8 
12-18 
54-85 
Diactine, probably marginal pinules (Plate 78 , fig. 3) have been observed 
only in the preparations of var. tenuis, form A, and var. lata. Their distal ray 
is usually pointed, exceptionally reduced in length, and rounded and thickened 
at the end (Plate 78 , fig. 3). It is covered with rather strongly inclined, distally 
directed, generally nearly straight spines. The proximal ray is usually more or 
less spiny, and pointed or rounded at the end. A central tyle, the remnant of 
the (reduced) lateral rays, is always present. It is irregularly spherical or com- 
posed of four distinct lobes (ray-rudiments). Generally it bears several large 
spines which point obliquely upward and outward. 
The dimensions of the diactine pinules are: — 
Distal ray 
total length 
length 
basal 
thickness 
n 
maximum 
thickness, to- 
gether with 
the spines 
M 
length of 
proximal 
ray 
transverse 
diameter of 
central tyle 
M 
var. 
tenuis 
form A 
400-610 
200-290 
5-10 
17-20 
190-320 
16-21 
var. lata 
410-490 
167-260 
6-9 
26-33 
160-260 
12-23 
Pentactine and hexactine spicules with very slender rays have often been 
observed in the interior of var. lata. I consider these spicules, which are con- 
nected with the microhexactines by numerous transitional forms, as canalar 
pinules. In these spicules one ray is different from, usually longer, rarely shorter, 
than, the others. This differentiated ray, which is to be considered as the distal, 
bears oblique, distally directed spines. The other rays are also spiny, but their 
spines are much smaller and generally situated vertically. The ray to be con- 
sidered as the distal is 100-170 /x long, 3.5-7 m thick at the base, and in its 
