218 HYALONEMA (HYALONEMA) PLACUNA. 
Mcsamphidiscs 
large 
medium 
small 
In form 
A 1 
B 
A 
B 
A< 
Bi 
Total length 
limits !>- 
197 
214-286 
105-186 
124-187 
55-100 
most 
frequently 
about /j 
249 
143 
163 
Thickness of shaft p 
5 
4-7 
2-4 
2-4 
1-2 
Diameter of central tyle p 
7 
6-11 
2. 8-6. 5 
3.5-6 
1.4-3. 5 
Length of terminal 
anchors 
limits n 
73 
71-130 
38-72 
40-82 
17-42 
most 
frequently 
about p 
108 
51 
63 
Maximum breadth 
of terminal anchors 
limits p 
54 
47-85 
19.5-52 
23-52 
10-24 
most 
frequently 
about p 
65 
31 
44 
Proportion of 
length to maximum 
breadth of terminal 
anchors 100 to 
limits 
73 
55-66 
43-66 
43-66 
42-59 
average 
58.9 
57 
54.7 
52.7 
whole spicule, and 6-11 p 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 p; length of terminal anchors 12-15 n; 
breadth of terminal anchors 6-6.5 p; 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. 37-41; Plate 65 , fig. 13) are 18.5-42 p long, most frequently 
26-32 p. The shaft is straight, 0.6-1 p thick, and either simple and cylindrical 
throughout (Plate 65 , fig. 13) or thickened somewhere near the middle to a 
central tyle 1-1.3 p 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 p long, a little less than a third to two fifths of 
Only one observed. 
2 Apparently absent. 
3 Only three observed. 
