320 
HYALONEMA (OONEMA) BIANCHGRATUM PINULINA. 
in their distal part, more rarely straight throughout. The curvature is such 
that the tangents of the end-parts of the rays enclose angles of 120°-150°, excep- 
tionally only 90°, with the continuation of the axis of their proximal parts. 
The proximal end-part of the rays is smooth for a short distance, the distal end- 
part for a considerable distance. The remaining, middle-part bears spines as 
much as 0.7 m long, which are generally vertical. As stated above, I think it 
probable that the straight-rayed microhexactines are canalaria, and only the 
curved-rayed ones true parenchymalia. 
In specimen b I found a microhexactine-derivate with only one ray. This 
monactine spicule appears as a spined tylostyle curved towards its pointed end. 
Its measurements are:- — length 105 m; basal thickness of single ray 4.5 m; 
tyle 8.5 m- 
Morphologically two kinds of amphidiscs can be distinguished : — those with 
stout shaft and relatively broad anchors; and those with slender shaft and rela- 
tively narrow anchors. 
To study them biometrically I measured 275 (134 of specimen a and 
141 of specimen b) and drew Figure 19, in which the length frequency-curves of 
the amphidiscs are represented as follows: — of specimen a ( ) ; of speci- 
men b ( ) ; and of both specimens together ( ) . 
In specimen a the amphidiscs are 18-480 m long. Their length frequency- 
curve ( ) exhibits two main elevations at about 33 m and about 164 n, 
a number of small elevations, and three large gaps between .54 and 79 m, between 
90 and 110 m, and between 200 and 220 m- The amphidiscs 18-54 m and 79- 
90 m long are all thin-shafted and narrow-anchored; those 110-200 m and 220- 
480 m long are all thick-shafted and broad-anchored. 
The amphidiscs of specimen b are 21.5-492 m long. Their length frequency- 
curve exhibits two main elevations corresponding exactly to the two main 
elevations of the curve for specimen 5; a number of small elevations, some 
of which correspond to the small elevations of b, and some of which do not so 
correspond; and three principal gaps between 66 and 79, 87 and 118 m, 
and 187 and 212 m- The amphidiscs 21.5-66 m and 79-87 m long all belong 
to the thin-shafted slender-anchored kind, those 118-187 m and 212-492 m 
long to the stout-shafted, broad-anchored kind. 
In both specimens therefore two main groups of amphidiscs can be dis- 
tinguished both morphologically and biometrically : — macramphidiscs with 
stout shaft and broad anchors, in both specimens together 110-492 m long, and 
micramphidiscs with thin shaft and slender anchors, in both specimens together 
