272 HYALONEMA (PRTONEMA) AZUERONE. 
more spiny shafts and relatively smaller and, on the whole, still more irregular 
anchors. The shaft is for the most part 1.2-2 n thick, and abruptly thickened 
in or near the centre to a remarkably large central tyle which measures 2-5 m in 
diameter. The remainder of the shaft is often not quite uniform in thickness. 
The proportion of the thickness of the shaft to that of the tyle is 100 to 133-333, 
on an average 100: 204.8. The whole of the shaft, including the central tyle, 
is beset with very numerous spines. Those on the tyle are either large and ar- 
ranged in a verticillate manner, or small and quite uniformly scattered over the 
whole tyle. Those on the remaining parts of the shaft are always small. The 
maximum length of the anchors is 7-12 /x, about a third of the length of the whole 
spicule, their breadth 8-12 n. The proportion of maximum length to breadth is 
100 to 73-125, on an average 100 : 101.3. The individual anchor-teeth are 
curved so that their end-parts do not greatly diverge from a direction parallel to 
the shaft. 
The slender-shafted micramphidiscs (Plate 57 , figs. 13-17; Plate 58 , fig. 12) 
are 30-58 n long, most frequently about 42 n- The shaft is regularly cylindrical, 
straight or, rarely, slightly curved, 1-1.7 m thick, and thickened at some point, 
sometimes a long way from the middle, to a central tyle 1.4-2. 4 \x in diameter. 
The proportion of the thickness of the shaft to that of the tyle is 100 to 114-131, 
on an average 100 : 121. A few blunt spines, sometimes 0.7 \i long, arise from 
the tyle. The remainder of the shaft is usually quite smooth. In a few, particu- 
larly in the large and slender-anchored ones, the shaft bears minute spines. The 
anchors are regular, 6-10 n long, a quarter to a sixth of the whole spicule, and 
9-10 n broad. The proportion of their length to their breadth is 100 to 105-150, 
on an average 100 : 121 .6. The number of teeth in the anchor is about seventeen. 
The individual teeth arise vertically and are considerably curved in their basal 
part. Distally the curvature decreases in a uniform manner. The end-parts 
of the teeth diverge more or less from the shaft. 
The large slender-anchored forms above referred to connect these amphi- 
discs with the small mesamphidiscs. 
The nearest ally of the sponge above described among the species hitherto 
made known appears to be Hyalonema validum F. E. Schulze. With this species 
it coincides in respect to the shape and size of all the spicules, with the excep- 
tion of the stout-shafted more or less irregular micramphidiscs, which are present 
in H. (P.) azuerone and absent in H. validum; the microhexactines, which have 
more strongly bent rays in the latter than in the former; and the dermal 
pinules, the distal rays of which are bushy and have a thick, abruptly pointed 
