HYALONEMA (PRIONEMA) AGUJAN^IM. 
263 
shaft (Plate 74, fig. 3; Plate 77, figs. 2, 3). The end-parts of the teeth are often 
bent rather abruptly inward and they generally converge. The teeth have the 
usual T-shaped transverse section. Their outer and upper band-shaped part 
is, in the larger serrated amphidiscs, nearly uniformly (18-22 M ) broad throughout, 
attenuated only slightly distally, and rounded at the end. The lateral and termi- 
nal margins of the teeth are bent down shaftwards and serrated. The serration- 
teeth are triangular, sharp-pointed, and usually directed more or less backwards. 
The lateral ones are 1.5-2 p long and 1-2 n broad, the terminal ones smaller. 
In var. tenuis, form A, and in var. lata the serrated amphidiscs attain a larger 
size than in var. tenuis, form B; and in var. lata the average relative breadth of 
the anchors is considerably greater than in the two forms of var. tenuis. The 
dimensions of the serrated amphidiscs are : — 
SERRATED AMPHIDISCS. 
var. tenuis. 
var. lata 
form A 
form B 
Total 
length 
limits fi 
90-410 
100-342 
90-415 
most frequently 
about ij. 
320 
103, 180 
149, 198, 264 1 
Shaft, thickness /x 
3-12 
5. 5-7. 5 
3.5-8 
Central 
tyle 
diameter ix 
6-17 
12-15 
6-14 
differences between 
diameter of tyle and 
adjacent parts of 
shaft n 
2.5-10 
6-8 
2-7.5 
Spines of 
central tyle 
length ix 
5-15 
8-12 
5-10 
basal thickness ix 
1.2-4 
1.5 
1-2 
Anchor 
length, limits /x 
30-159 
30-145 
60-165 
breadth, limits /x 
20-120 
25-118 
48-154 
Proportion of 
anchor-length to 
anchor-breadth 
limits 100: 
63-106 
55-83 
63-105 
average 100 : 
71.8 
70.4 
83 
Proportion of 
anchor-length to 
total length of the 
whole spicule 
limits 1: 
2-2.4 
2. 2-2. 4 
2.2-2. 4 
average 1 : 
2.3 
2.3 
2.3 
1 When there are two or more numbers in this zone it indicates that the length frequency-curve 
pertaining to the spicules of the variety or form has more pronounced elevations than one; in these the 
serrated amphidiscs do not appear to be biometrically homogeneous groups, 
