276 
HYALONEMA (PRIONEMA) SPINOSUM. 
The abundant normal large macramphidiscs (Plate 48 , figs. 14-16; Plate 49 , 
figs. 7-9, 11 ; Plate 50, figs. 1-5) are 180-298 n long, most frequently about 255 /z. 
The shaft is usuallj r straight, rarely slightly curved, for the most part nearly 
cylindrical, 3-8 n thick, and abruptly thickened at or near the middle to a 
central tyle 6.5-17 n in transverse diameter. The proportion of the diameter 
of the adjacent parts of the shaft to the diameter of the tyle is 1 : 1.3 — 1 : 3.2, 
most frequently about 1 :2. From the central tyle a verticil of about eight- 
large spines arises; these are slightly and irregularly curved but on the whole 
vertical (Plate 48 , figs. 14-16; Plate 49 , figs. 8, 9, 11). These spines are cylin- 
drical, rounded or abruptly pointed at the end, and always quite smooth and 
destitute of secondary spinelets. They are 8-23 n long and 2-3.5 n thick at the 
base. The parts of the shaft outside the central tyle and its vicinity bear nu- 
merous low, cylindrical and truncate, wart-like spines, 0.5-1. 5 m high, 1-2 n broad, 
and circular in outline (Plate 48 , figs. 15, 16; Plate 49 , figs. 8, 9, 11). From the 
terminal face of each of these spines a cluster of exceedingly minute secondary 
spinelets arises. 
The terminal anchors are 68-107 n long, considerably more than a third of 
the whole spicule, and 61-117 /x broad. The proportion of length to breadth is 
100 : 73-100 : 114, on an average 100 : 94. A correlation between the anchor- 
proportion and the size of the spicule was not noticed. All the anchors counted 
were composed of eight teeth. 
The individual teeth are considerably curved near the base. Distally the 
curvature decreases. The end is slightly and somewhat abruptly bent inward 
towards the shaft. The teeth have a T-shaped transverse section. The upper 
part is band-shaped, 9-13 n broad near the base, very slightly attenuated distally, 
and rounded at the end. The lower part is a crest projecting towards the shaft. 
This crest is 5 n high near the base; distally it gradually becomes lower, and it 
appears to vanish altogether about 10 m from the end of the tooth. The anchor- 
teeth bear, on their lateral margins, secondary teeth and consequently appear 
serrated (Plate 49, fig. 7; Plate 50, figs. 1-5). These secondary teeth stand 
quite close together and extend from the base to within a short distance of the 
end of the primary tooth, leaving only the rounded end free. The secondary 
teeth are triangular in outline, 0.5-1. 2 n long, 1-1.5 n broad, sharp-pointed, and 
directed more or less backwards. They resemble shark’s teeth. 
Besides the normal spicules above described a few young and also a few 
abnormally large macrampkidiscs have been observed. The young forms have a 
slender shaft, a relatively stout central thickening, and short and thin anchor- 
