218 HYALONEMA (HYALONEMA) PLACUNA. 
Mesamphidises large medium small 
In form Al B A B A? B3 
limits 4 197 214-286 105-186 124-187 55-100 
Total length most 
frequently 249 143 163 
about / 
Thickness of shaft » 5 4-7 2-4 2-4 1-2 
Diameter of central tyle 7 6-11 2.8-6.5 3.5-6 oe 
limits 73 71-130 38-72 40-82 17-42 
Length of terminal 
ee most 
as frequently 108 51 63 
about 
limits 54 47-85 19.5-52 23-52 10-24 
Maximum breadth 
of terminal anchors mie 
= : frequently 65 31 44 
about / 
Proportion of Pa 3 
. limits 73 55-66 43-66 43-66 42-59 
length to maximum 
breadth of terminal |— SS 
anchors 100 to average 58.9 57 54.7 52.7 
whole spicule, and 6-11 » broad. The proportion of their length to their breadth 
is 100 to 50-56, on an average 100 : 52.3. The individual teeth arise vertically 
from the shaft, and are strongly bent in their proximal, and fairly straight in their 
distal part. Their straight end-parts are usually parallel to the shaft. 
In form A these spicules (Plate 63, fig. 42) are similar in shape, but smaller 
and provided with somewhat narrower anchors. Their dimensions are here 
the following: — total length 28-38 4; length of terminal anchors 12-15 y; 
breadth of terminal anchors 6-6.5 4; proportion of anchor-length to anchor- 
breadth 100 to 43-50, on an average 100 : 47.5. 
The small micramphidiscs with broad anchors are abundant. Those of form B 
(Plate 63, figs. 837-41; Plate 65, fig. 13) are 18.542 u long, most frequently 
26-32 ». The shaft is straight, 0.6-1 » thick, and either simple and cylindrical 
throughout (Plate 65, fig. 13) or thickened somewhere near the middle to a 
central tyle 1-1.3 » in diameter. This tyle and the middle-part of the shaft 
usually bear some minute low and broad spines, either on all sides or on one side 
only. The anchors are 6-16 u long, a little less than a third to two fifths of 
1 Only cne observed. * Apparently absent. 3 Only three observed. 
