326 
HYALONEMA (OONEMA) BIANCHORATUM PINULINA. 
The chief dimensions of the S7nall micramphidiscs (Plate 84 , figs. 15-25) 
are : — 
of specimen 
a 
of specimen 
6 
of both speci- 
mens together 
Length n 
limits 
18-54 
21.5-66 
18-66 
most frequently about 
33 
33 
33 
Shaft, thickness, limits /u 
1-1.7 
1-2.5 
1-2.5 
Central 
transverse diameter of tyle, limits ju 
1-3 
1-4.5 
1-4.5 
tyle 
the tyle thicker than the shaft by, limits n 
0-1.6 
0-2.5 
0-2.5 
length, limits n 
7-20 
6.5-23.5 
6.5-23.5 
breadth, limits n 
7-17 
8 . 5-23 
7-23 
Terminal 
anchors 
proportion of anchor- 
length to anchor- 
breadth 
limits 100 to 
77-128 
80-146 
77-146 
average 100 to 
97.4 
102.6 
100.6 
proportion of anchor- 
length to total length 
of whole spicule 
limits 1: 
2.7-4 
average 1: 
3.2 
In these amphidiscs the shaft is usually straight, rarely curved. In some 
place at or near the middle it is thickened, gradually in the larger, more abruptly 
in the smaller, to a rather stout central tyle. In the larger forms the tyle and the 
adjacent parts of the shaft, about one third of its total length, are densely cov- 
ered with spines sometimes 1 ^ long. The end-parts of the shaft of these am- 
phidiscs are smooth or only roughened by exceedingly minute spines. In the 
smaller forms the spines on the shaft are so small that they can hardly be made 
out as such, and merely render the shaft somewhat rough in appearance. 
The anchor-teeth are curved rather strongly in their proximal part, but 
only slightly or not at all in their distal part. Their end-parts are generally 
slightly divergent. 
A few abnormal small micramphidiscs were found in specimen b. In one 
of these, 26 m long, a straight cylindrical branch arises very obliquely from 
the shaft. This branch is as thick (1.6 m) and half as long as the shaft, and 
broken off at the end. In another small micramphidisc (45 m long, with termi- 
nal anchors 19 n long and 22 /x broad), two opposite rays lying in the same 
straight line and both vertical to the shaft arise from the centrum of the spi- 
cule. These rays are straight, as thick as the shaft (2 n), and, like the shaft, 
