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HYALONEMA (HYALONEMA) POLYCAULUM. 
and the large and small micramphidiscs of Hyalonema (. Hyalonema ) obtusum ) 
can be distinguished : — macramphidiscs, large micramphidiscs, and small 
micramphidiscs. 
The macramphidiscs (Plate 53 , figs. 1-3, 13; Plate 54 , figs. 28, 29) are 200- 
365 n long, most frequently about 293 //. The shaft is cylindrical, straight, 
6.5- 12 n thick, and abruptly thickened in or near the middle to a central tyle 
12-18 n in diameter. The proportion of the thickness of the adjacent parts of 
the shaft to the thickness of the tyle is 100 n to 115-170. A verticil of truncate 
or blunt-pointed, often irregularly curved spines 3.5-7 n long and 2.5-4 n 
thick arises from this tyle. Spines similar in shape but smaller (particularly 
shorter, only 1.5-3 n long and 2-3 ij thick) are scattered in larger or smaller 
numbers over the other parts of the shaft. The tips of the spines are smooth 
or slightly roughened. The terminal anchors are 60-100 n long, usually consid- 
erably less than a quarter of the whole spicule, and 67-107 n broad. The pro- 
portion of their length to their breadth is 100 to 103.8-125.7, on an average 100: 
115.5. They consist of ten to twelve teeth. The individual teeth are curved 
in their (shorter) proximal part and generally nearly straight in their (longer) 
distal part. The latter usually diverges considerably and encloses an angle of 
about 20° with the shaft. The teeth are T-shaped in transverse section. Their 
upper part appears as a band about 10 /z broad and is abruptly attenuated 
to a point at the end. 
The large micramphidiscs (Plate 53 , figs. 5, 6; Plate 54 , figs. 26, 27) are 
30-56 n long. The shaft is straight, 1.2-1. 7 n thick, and gradually thickened 
in a spindle-shaped manner in or near the middle. It bears a few small cylindri- 
cal spines. Some of these always arise from the central thickening. The 
anchors are usually 13.5-17 n long, generally considerably more than one third 
of the whole spicule, and 8-10 n broad. The distal parts of the individual teeth 
are fairly straight and generally nearly parallel to the shaft. 
The small micramphidiscs (Plate 53 , fig. 7 ; Plate 54 , figs. 21-25) are 13-27 n 
long, most frequently about 19.5 n. The shaft is straight, cylindrical, and 
0.7-1. 5 n thick. Its central part usually bears a few spines. The anchors are 
4. 5- 7. 5 m long, usually a quarter to a third of the whole spicule, and 5-8 fx broad. 
The individual anchor-teeth, of which there are about eighteen in one anchor, 
are more strongly curved some distance from the base than elsewhere. The 
end-part is nearly straight, and diverges very slightly or not at all from the shaft. 
The spiculation of the four hard superficial knobs indicates that the sponge 
above described had at least two, probably four, distinct and distant stalks, each 
composed of a separate bundle of spicules. 
