HYALONEMA (HYALONEMA) GRANDANCORA. 
237 
The hexactines (Plate 79 , figs. 13-19) are 0.4-3 mm. in diameter, and have 
nearly equal or somewhat unequal, conical and pointed, straight or slightly 
curved rays 10-80 n thick at the base. 
The rhabds are centrotyle, generally more or less curved, 0.8-1. 3 mm. long 
and 10-20 m thick. The central tyle is 1-3 n more in transverse diameter than 
the adjacent parts of the spicule. 
Among the acanthophores the diactines and tetractines are much more 
frequent than the others. In the entirely spined forms the rays are shorter and 
thicker than in the ones with rays spined only terminally. The dimensions of 
these spicules are the following : — 
with 1 or 2 rays; more 
or less rod-shaped 
with 3 more or less equally 
developed rays 
with 4 or 5 more or less 
equally developed rays 
Acanthophores 
total length 
M 
thickness of 
rays 
M 
total length 
M 
thickness of 
rays 
M 
total length 
A* 
thickness of 
rays 
with rays spined only at 
the end 
154-1100 
10-41 
285-385 
18-28 
120-350 
9-26 
entirely spined 
85-290 
28-58 
147 
30 
90-152 
20-26 
In the rod-shaped monactines and diactines which are only terminally spined 
an inverse proportion between length and thickness is clearly pronounced: — 
the spicules of this kind 154-400 p long are 26-41, on an average 29.7 n thick 
“ “ “ “ “ 401-550 M “ “ 19-26, “ “ “ 22.5 M “ 
“ “ “ “ “ 551-1100 n “ “ 10-23, “ “ “ 15.2 m “ 
The entirely spined spicules of this kind exhibit a similar relation between 
length and thickness : — 
those 85-120 m long are 35-58, on an average 43.3 n thick 
“ 121-290 M “ “ 28-31, “ “ “ 29 M “ 
The long and slender diactines which are only terminally spined have a 
central tyle 2-8 m more in transverse diameter than the adjacent parts of the 
spicule. In some of the shorter and stouter ones the tyle is relatively larger. 
The spines are broad and conical. In the entirely spined forms they are usu- 
ally about 7 m, very rarely as much as 10 n, long and broad; in those with rays 
only terminally spined they are smaller. 
Besides these spicules a few pinule-like, entirely spined pentactine and 
hexactine acanthophores with one differentiated ray were found in the basal 
part of the sponge. The dimensions of these spicules, which I consider as pinule- 
