LANUGON YCH I A FLABELLUM. 
107 
These hexac tines and hexactine-derivates measure 134-318 m in total 
diameter. Their fully developed rays are 83-180 n long and 5-14 n thick at the 
base. They are usually regularly conic and sharp-pointed, rarely cylindro- 
conic and somewhat blunt. The reduced rays are 6-25 long, 7-16 n thick, 
cylindrical, and terminally rounded. The length and thickness of the properly 
developed rays is, as the subjoined table shows, in the monactine to pentactine 
forms in inverse proportion to their number. The hexactine forms apparently 
do not conform to this rule. Since, however, the state of preservation of the 
specimen renders it impossible to ascertain clearly whether the not numerous 
larger hexactines are choanosomal or superficial, it might be assumed that these 
large hexactines are choanosomal spicules and do not belong to the series repre- 
sented by the dermals and gastrals, to which that rule applies. The small 
hexactines conform to the rule, and some at least of these are certainly superficial. 
HEXACTINES AND PENTACTINE TO MONACTINE HEXACTINE-DERIVATES. 
Fully developed rays 
Number 
Length 
Basal thickness 
limits n 
average of the 
longest three ,u 
limits /x 
average of the 
thickest three /x 
6 
83-140 
132 
5-10 
9 
5 
90-118 
114 
5-9 
8 
4 
95-125 
120 
6-9 
8 
3 
100-142 
141 
5-11 
10 
2 
105-160 
152 
6-11 
10 
1 
123-190 
1S5 
10-14 
13 
Both the fully developed and the reduced rays are covered with spines. 
On the basal parts of the fully developed rays the spines are somewhat sparse 
and here they arise vertically. On their distal parts the spines are more numer- 
ous and here they point obliquely outward. The extreme tip of the ray is 
usually free from spines for a distance of 4 or 5 /x- The spines are conic, sharp- 
pointed, and 0.5-2 ^ high. Their size is in proportion to the thickness of the ray 
from which they arise, the stoutest rays bearing the largest spines. 
The cylindrical, terminally rounded, more or less knob-like, reduced rays 
are covered with similar spines, which are either similarly distributed as on the 
fully developed rays or more crowded. 
