264 HYALONEMA (PRIONEMA) AGUJANUM. 
The rare large micramphidiscs have a stout shaft with an exceptionally 
large, usually somewhat irregular, central tyle. This tyle bears numerous 
minute and slender spines. These are not arranged in a verticillate manner, 
but are scattered over the whole tyle. The remaining parts of the shaft also ~ 
bear minute spines. The anchor-teeth, which arise nearly vertically from the 
end of the shaft, are curved quite uniformly throughout, through an angle of 
about 90°, so that their end-parts are nearly parallel. The dimensions of these 
amphidises are: — 
LARGE MICRAMPHIDISCS. 
var. tenuis 
var. lata 
form A form Bt 
limits yu 51-80 47,78 47-64 
Total 
length most frequently 75 50, 60 
about yu 
Shaft, thickness 1.3-3 ioe 
diameter yp 4-7 3.5 5.5 
Central differences between 
tyle diameter of tyle and 27-4 3-4 
adjacent parts of 
shaft 
length, limits 18-39 13, 35 | 18-24 
Anchor = “- 
breadth, limits 17-31 11, 26 14-20 
Proportion of “limits 100: 67-100 | 74-85 | 78-83 
anchor-length to — SS 
anchor-breadth average 100: 82.5 79.5 | 80.5 
ee | eS ee eee ee, S| | 
Proportion of a | 
anchorlenet ito | limits 1: 2-3 2.2,3.7 2.3-3 
total length of the | ; | 
spicule | average 1: 2.5 2.9 72,0 
The small micramphidiscs (Plate 75, figs. 24-27, 31-34; Plate 77, fig. 8) 
have a straight shaft, which is either simple, cylindrical, and without any trace 
of a central tyle, or, more rarely, slightly thickened at or near the centre to a 
small central tyle. Such central tyles on the shaft are much more frequent in 
the small micramphidises of var. lata than in those of var. tenuis. The shaft is 
covered throughout with more or fewer, sometimes very numerous minute spines. 
1 Only two seen. 
