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 ^i. The shaft is straight, centrotyle, and 

 1.5-4 M thick. The central tyle is 2-5 /i in transverse diameter, that is 0.5-2.5 m 

 more than the adjacent parts of the shaft. The shaft bears rather numerous 

 scattei'ed spines, the largest of which arise from the central tyle. These spines 

 are 1-^ /x long and, if long, generally considerably curved. The terminal anchors 

 are 13-31 tx long, usually about a third of the whole spicule, and 15-35 m 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 /x long, most frequently about 26.8 m- The shaft is straight, usually 

 distinctly centrotyle, and 1-1.7 yu thick. The tyle is 1.5-2.3 yu in transverse 

 diameter, that is 0.2-1.2 ^ more than the adjacent parts of the shaft. The termi- 

 nal anchors are 7-16.5 fj. 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 ^i long, has a shaft 1.5 ^ 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 alUes of the above sponge are the species Hyalonema (Oonema) 

 sequoia, H. (0.) crassipinulum, and H. (0.) 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. 



