HYALONEMA (PRIOXEMA) PINULIFUSUM. 293 



The large short-anchored micram-phidiscs (Plate 72, fig. 15) are 33.5-62 n 

 long, most frequently about 44 ^. The shaft is 0.9-2.8 ^ thick, and usually 

 thickened at or near the middle to a central tyle, which is sometimes 1.1 /n more 

 than the adjacent parts of the shaft in transverse diameter. In many of these 

 spicules the tyle is very insignificant, and in some not a trace of a central tyle 

 could be detected. The shaft usually bears minute scattered spines, the most 

 conspicuous of which arise from the central tyle. 



The anchors are 5-24 ^l long, usually about a quarter of the whole spicule, 

 and 8-17 m broad. The proportion of their length to their breadth is 100 to 

 71-160, on an average 100 : 109.3. The individual teeth are curved rather 

 uniformly throughout. Their ends are more or less divergent. 



The small long-anchored inicramyhidiscs (Plate 72, figs. 9-14) have remark- 

 ably stout shafts. They are 15-35 m long, most frequently about 20 m- The 

 shaft is straight, 1.2-2.5 m thick, and frequently thickened at one place to a 

 spindle-shaped "central" tyle, sometimes 1 ix more than the adjacent parts of 

 the shaft in transverse diameter. This tyle is usually situated very eccentri- 

 cally. In the larger forms the shaft bears numerous conspicuous spines (Plate 

 72, fig. 14). In the smaller ones the spines are fewer in number and smaller 

 in size; sometimes they are absent altogether. 



The anchors are 5-16 m long, about a third of the whole spicule, and 6-13 n 

 broad. The proportion of their length to their breadth is 100 to 77-200, gen- 

 erally 100 to 83-140, on an average 100 : 112.3. The anchor-teeth are curved 

 towards the shaft quite strongly in their basal part, and less strongly or not at all 

 in their distal part. The tips of the teeth (their distal straight parts) are nearly 

 parallel to the shaft. 



Its fragmentary nature renders it impossible to say with certainty to which 

 genus of the Amphidiscophora this sponge belongs. The chief reason for placing 

 it in Hyalonema (Prionema) is the presence of serrated amphidiscs and the gen- 

 eral resemblance of its spiculation to that of some of the species of this genus. 

 Its nearest allies appear to be Hyalonema hercules F. E. Schulze,^ and H. (P.) 

 agujanum (p. 251). Hyalonema hercules resembles it in its general appearance, 

 but differs from it in respect to its macramphidiscs and gastral pinules. In H. 

 hercules the macramphidiscs have four large spines, arranged crossways, on the 

 central tyle, and the gastral pinules have very long and slender distal rays. In 

 the sponge above described the tyles of the macramphidiscs bear only from one 

 to three quite insignificant spines, and there are no such pinules with long and 



1 F. E. Schulze. Amerikanische Hexactinelliden, 1899, p. 9, taf. 1, figs. 19-29. 



