194 
HYALONEMA (HYALONEMA) AGASSIZI. 
they are more abundant is Monorhaphis dives, 1 where they usually have six 
anchor-bearing rays. F. E. Schulze iloc. cit.) named these spicules hexadiscs. 
The spicule above described and others similar, like the one found in Hyalonema 
tenerum ( loc . cit.), might, in an analogous manner, be called tetradiscs, or stauro- 
discs. 
In the other forms of Hyalonema agassizi only a few small macramphidiscs 
have been observed. Those seen were similar but smaller than those of form A. 
The small macramphidiscs of form B (Plate 45 , fig. 53) are 53-101 n long. Their 
shafts are 2-4 p thick, and their anchors 18-27 /x long and 18-33 n broad. Those 
of form C are 53-80 /x long. Their shafts are 2-3.3 n thick, and their anchors 
20-24 p long and 16.5-20 m broad. In form D only a single small macramphi- 
disc was found. This was 84 p long. 
In form E the small macramphidiscs are 48-90 /x long, most frequently about 
51 m, and have anchors 10-33 m long and 10-25 /x broad. In form F I found only 
two such spicules. These were 45 and 70 n long respectively. 
In form A the large micramphidiscs (Plate 45 , figs. 46-49; Plate 47 , figs. 11- 
13) are very numerous. They are here 42-60 /x long, most frequently about 
52.3 ii. The shaft is 1.1-2 /x thick, cylindrical, or slightly and very gradually 
thickened, in a spindle-shaped manner, in or near the middle, but without a 
sharply defined central tyle. It is covered with numerous, slender, cylindrical, 
vertical or, more rarely, oblique spines, sometimes 2 n long. The anchors are 
relatively slender. They are 14.4-22 p long, that is a little more than a third 
of the whole spicule, and 8-14 m broad. The proportion of their length to their 
breadth is 100 : 53 (in one of the smallest), 100 : 71 (in one of the largest), on 
an average 100:65. The individual anchor-teeth are about 1.5 /x broad and 
strongly curved, so that their end-parts lie nearly parallel to the shaft or converge 
towards it. 
In form B, where they are rather scarce, the large micramphidiscs appear 
to be similar to those of form A, and measure 41-59 m in length, most frequently 
about 54.8 p. 
In form C (Plate 45 , figs. 59-61), where they are still more numerous than 
in form A, they measure 36-64 p in length, most frequently, as those of form A, 
about 52.3 p in length, and have spinecl shafts 1-1.7 m thick. Their anchors are 
17-23 m long and 10-13 /x broad. One in which I was able to count the anchor- 
teeth had fourteen. The individual teeth in the larger forms are about 2.5 ^ 
broad. 
1 F . E. Schulze. Hexactinellida. Ergeb. Deutsch. t.iefsee-exped., 1904, 4 , p. 124, taf. 43, figs. 1, 6, 7. 
