HYALONEMA (PRIONEMA) AZUERONE. 269 
small regular anchors; and D small amphidises with stout shafts and relatively 
large, usually more or less irregular anchors. Biometrically, according to 
the length frequency, A is a well-defined, simple, and homogeneous group. 
B overlaps C and D somewhat, and C and D are about equal in length. B 
is biometrically composed of three secondary groups represented by (a), large, 
(b), medium sized, and (c), small amphidises. C is biometrically a simple 
and homogeneous group. JD is biometrically composed of two well-defined 
secondary groups represented by larger amphidises (a), and smaller amphi- 
dises (b). Thus if both their shape and the biometric character of their length- 
frequencies are taken into consideration seven kinds of amphidises are to 
be distinguished:— macramphidises (A); large mesamphidises (B a); medium 
mesamphidises (B 6b); small mesamphidises (Be); slender-shafted micram- 
phidises (C); stout-shafted large micramphidises (D a); and stout-shafted small 
micramphidises (D b). 
The macramphidiscs (Plate 57, figs. 1-5; Plate 58, figs. 5-9) are 300-356 u 
long, most frequently about 320 4. Their shaft, which is straight and for the 
most part 7-9 u thick, thickens at the ends gradually to a conic extension 10-14 yu 
in diameter, and in or near the middle abruptly to a central tyle of the same 
diameter. The proportion of the thickness of the adjacent parts of the shaft 
to the thickness of the central tyle is 100 to 130-200, on an average 100 : 157.4. 
An irregular verticil of cylindroconic, truncate, or terminally rounded spines arises 
from the central tyle. These spines are 1.5-3.5 w thick, usually 1.5-4 uw long, 
sometimes as much as 8», and when long are irregularly curved. They bear 
on their terminal face a cluster of exceedingly minute secondary spinelets. 
Seattered spines, similar to those of the central tyle, but on the whole shorter, 
are met on the remaining parts of the shaft. The terminal anchors are 77— 
119 » long; they are broadest usually a little over a third of the whole spicule, 
somewhere beyond the middle, and attenuated towards the end. Their maxi- 
mum breadth is 85-104 yu, their end-breadth 75-95 ». The proportion of length 
to maximum breadth is 100 to 77-114, on an average 100: 101.5. The maxi- 
mum breadth is 3-11 », on an average 7.1 uw, greater than the end-breadth. The 
anchor usually consists of nine or ten teeth. The individual teeth arise steeply 
from the end of the shaft, and are strongly curved in their basal part. Farther 
on the curvature decreases either gradually or somewhat abruptly. The 
‘decrease of curvature either continues to the end of the tooth, or it increases 
again just before the end. The total curvature is such that the end-parts of 
the teeth converge toward the shaft, with the axis of which they usually enclose 
