HYALONEMA (PRIONEMA) AGUJANUM. 
261 
either parallel, or slightly convergent or divergent. The teeth have the usual 
T-shaped transverse section. Their upper (outer) band-shaped part arises 
from the margin of a transverse circular disc situated at the end of the shaft. 
The diameter of this disc is a little less than a third of the anchor-breadth. In 
apical views of the anchors, the basal parts of adjacent teeth appear connected 
by the interdental parts of this disc as by a web (Plate 77, fig. 10). The upper 
band-shaped part of the teeth is 22-27 n broad at the base and in the middle. 
It is attenuated distally and pointed at the end. The contour of the tip of the 
tooth has the shape of a gothic arch (Plate 73, figs. 1-3; Plate 77, fig. 9). 
The macramphidiscs have on the whole narrower anchors and attain a 
considerably larger size in var. tenuis, form A, than in var. tenuis, form B, and 
in var. lata. Their dimensions are as follows : — - 
NORMAL MACRAMPHIDISCS. 
Hyalonema ( Prionema ) agujanum 
var. tenuis 
var. lata. 
form A. 
form B. 
Total 
length 
limits fx 
225-440 
200-350 
207-370 
most frequently 
about ix 
387 
320 
320 
Shaft, thickness ix 
20-27 
18-22 
19-25 
Central 
tyle 
diameter /x 
28-43 
26 
24-34 
difference between 
diameter of tyle and 
adjacent parts of 
shaft ix 
4-19 
5 
2-11 
Spines of 
central tyle 
length n 
5-15 
9 
4-7 
basal thickness ix 
8-11 
10 
5-9 
Anchor 
length, limits ix 
63-110 
55-83 
65-95 
breadth, limits n 
116-172 
119-160 
112-168 
Proportion of 
anchor-length to 
anchor-breadth . 
limits 100 : 
143-221 
171-236 
155-211 
average 100: 
• 
169 
1 
196 
186.8 
Proportion of 
anchor-length to 
total length of 
whole spicule 
limits 1 : 
3. 9-5. 4 
4. 2-4. 9 
3.1-5 
average 1: 
4.7 
4.7 
4.2 
