HYALONEMA (OONEMA) BIANCHORATUM PINUL1NA. 
325 
inner contour (the inner margin of the keel) and the lateral margin, on the 
other hand, diverge from the shaft. 
In specimen a I found a remarkable abnormal small macramphidisc (Plate 
85 , fig. 8) 190 m long, with terminal anchors respectively 80 and 100 n long and 
about 100 m broad. In this spicule each anchor is composed of two partly 
incomplete and somewhat irregular verticils of anchor-teeth, instead of a regu- 
lar single one. This duplication is much more pronounced in one (the upper one 
in the figure) than in the other terminal anchor. Some of the teeth belonging 
to the inner (supernumerary) verticils are nearly straight, extend obliquely 
backwards, and are widened at the end to irregularly oval terminal discs. The 
position of these terminal discs is such that if the whole amphidiscs were assumed 
to be enclosed in a tight-fitting ovoid mantle or shell, the outer faces of the 
terminal discs would come to lie exactly in the (inner) surface of such mantle 
or shell. This observation seems to me to be of similar import as the one on 
an abnormal amphidisc found in Hyalonema ( Prionema ) agujanum var. tenuis 
(p. 262, Plate 75 , figs. 35-37); both favor the view that each amphidisc is 
formed within a single ovoid cell. 
The chief dimensions of the large micr amphidiscs are: — 
of specimen 
a 
of specimen 
b 
of both speci- 
mens together 
Length p 
limits 
79-90 
79-87 
79-90 
most frequently about 
85 
82 
84 
Shaft, thickness, limits p 
4 
3.5 
3.5-4 
Central 
transverse diameter of tyle, limits p 
4 
4 
tyle 
the tyle thicker than the shaft by, limits yu 
0.5 
0.5 
length, limits /x 
26-35 
26-29 
26-35 
breadth, limits yu 
23-40 
23-25 
23 40 
Terminal 
anchors 
proportion of anchor- 
length to anchor- 
breadth 
limits 100 to 
80-114 
83-88 
80-1 14 
average 100 to 
79 
86.3 
91.2 
proportion of anchor- 
length to total length 
of whole spicule 
limits 1: 
2. 4-3. 2 
average 1: 
2.8 
In these amphidiscs the shaft is straight. The central tyle is not defined 
and passes gradually into the adjacent part of the shaft. Tyle and shaft are 
very spiny. 
