290 HYALONEMA (PRIONEMA) PINULIFUSUM. 
I. Macramphidiscs (1) 
II. Mesamphidiscs 
A serrated mesamphidiscs 
a large serrated mesamphidiscs (2) 
b small serrated mesamphidiscs (3) 
B smooth mesamphidiscs 
a large smooth mesamphidiscs (4) 
b small smooth mesamphidiscs (5) 
III. Micramphidiscs. 
A larger short-anchored micramphidiscs (6) 
B smaller long-anchored micramphidiscs (7) 
The macramphidiscs (Plate 71, figs. 5-8) are 370-470 n long, most frequently 
about 425 yu. The shaft is straight, for the greater part of its length cylindrical, 
and 15-22 n thick. It is gradually thickened towards the ends, and generally 
also slightly and somewhat abruptly thickened near the middle to a central 
tyle. The ends usually exceed the thinnest part of the shaft by 9-12 n in thick- 
ness. The central tyle is small, or absent altogether, and measures, when 
present, 18-29 yu in transverse diameter, that is 1-9.5 n more than the adjacent 
parts of the shaft. The shaft is very poor in spines. Sometimes it bears no 
spines at all. Usually one to three cylindrical and truncate, or cylindroconical 
and terminally rounded spines arise from the central tyle, or, when it is absent, 
from a corresponding point of the shaft. These spines are 4-11 /j. long and 
3-9 yu thick. The remaining parts of the shaft are either quite smooth or bear 
one or a few spines similar to the central ones. 
The anchors are 126-162 n long, about a third of the whole spicule, and 153- 
177 m broad. The proportion of their length to their breadth is 100 to 103-138, 
on an average 100 : 115.3. They are composed of eight teeth. The individual 
teeth have the usual T-shaped transverse section. The upper (outer) part of 
the teeth, which corresponds to the upper stroke of the T, is band-shaped, 24- 
29 /x broad, and abruptly pointed or rounded at the end. The margins of these 
bands, that is the lateral margins of the teeth, are either smooth throughout, 
or they exhibit slight irregularities, sometimes even an indication of a serration, 
in their distal part. The lower (inner) part, which corresponds to the lower 
stroke of the T, is, at the base of the tooth, usually 19-22 /x high. The teeth 
arise nearly vertically from the shaft, and are curved downward in such manner 
that their ends are either parallel or convergent. In the latter case the anchor is, 
at the end, sometimes 17 yu narrower than in its broadest part, above. 
