194 HYALONEMA (HYALONEMA) AGASSIZI. 



they are more abundant is Monorhaphis dives, ^ where they usually have six 

 anchor-bearing rays. F. E. Schulze {loc. cit.) named these spicules hexadiscs. 

 The spicule above described and others similar, like the one found in Hyalonema 

 tenerum {luc. 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 ix thick, and their anchors 18-27 ^ long and 18-33 ^ broad. Those 

 of form C are 53-80 ^ long. Their shafts are 2-3.3 /x thick, and their anchors 

 20-24 ft long and 16.5-20 /j. broad. In form D only a single small macramphi- 

 disc was found. This was 84 n long. 



In form E the small macramphidiscs are 48-90 ^ long, most frequently about 

 51 M, and have anchors 10-33 m long and 10-25 m broad. In form F 1 found only 

 two such spicules. These were 45 and 70 ju 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 n long, most frequently about 

 52.3 /J. The shaft is 1.1-2 n 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 ^ long. The anchors are 

 relatively slender. They are 14.4-22 yu long, that is a little more than a third 

 of the whole spicule, and 8-14 ix 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 ^ broad and 

 strongly curved, so that their end-i)arts 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 ^ in length, most frequently 

 about 54.8 ju- 



In form C (Plate 45, figs. 59-61), where they are still more numerous than 

 in form A, they measure 36-64 ju in length, most frequently, as those of form A, 

 about 52.3 n in length, and have spined shafts 1-1.7 ^ thick. Their anchors are 

 17-23 M long and 10-13 m 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. tiefsee-exped., 1904, 4, p. 124, taf . 43, figs. 1, 6, 7. 



