348 
HYALONEMA (OONEMA) DENSUM. 
The large micramphidiscs (Plate 95 , figs. 5-8) are abundant. They are 44- 
86 n long, most frequently about 69.5 m - The shaft is straight, centrotyle, and 
1.5-4 n thick. The central tyle is 2-5 n in transverse diameter, that is 0.5-2. 5 n 
more than the adjacent parts of the shaft. The shaft bears rather numerous 
scattered spines, the largest of which arise from the central tyle. These spines 
are 1-4 n long and, if long, generally considerably curved. The terminal anchors 
are 13-31 n long, usually about a third of the whole spicule, and 15-35 n broad. 
The proportion of anchor-length to anchor-breadth is 100 to 78-123, on an aver- 
age 100 : 102.3. The individual teeth are curved rather strongly in their basal 
part. Distally the curvature decreases so that their ends are slightly divergent 
or nearly parallel. 
The small micramphidiscs (Plate 95 , figs. 9, 10) are not numerous. They 
are 24-40 n long, most frequently about 26.8 n. The shaft is straight, usually 
distinctly centrotyle, and 1-1.7 n thick. The tyle is 1.5-2. 3 n in transverse 
diameter, that is 0.2-1. 2 n more than the adjacent parts of the shaft. The termi- 
nal anchors are 7-16.5 n long, usually less than a third of the whole spicule, 
and 7-14 n broad. The proportion of anchor-length to anchor-breadth is 100 
to 75-143, on an average 100 : 97.8. The individual teeth arise vertically from 
the ends of the shaft, are straight in their basal part, curved through a quadrant 
in their middle-part, and straight again in their distal part. Their ends are 
parallel. 
Among the small micramphidiscs I found several irregular ones with asym- 
metric anchors. One of these is 16 n long, has a shaft 1.5 n thick, and possesses 
apparently only two teeth, one in each anchor. These two teeth stand opposite 
each other and are not very much shorter than the whole spicule, which is 
consequently similar to a depressed S. 
The nearest allies of the above sponge are the species Hyalonema ( Oonema ) 
sequoia, H. ( O .) crassipinulum, and II . (O.) henshawi described in this Report. 
From these it differs by the smaller size, and the distinct curvature of the rays 
of its micramphidiscs; by the possession of acanthophores with terminally 
rounded spines; by differences in the dimensions of its pinules; and by the shape 
and general density of its body. 
