244 HYALONEMA (HYALONEMA) SP. 



The acanthophores (Plate 80, fig. 13) have one to four more or less fully 

 developed rays. The tri- and tetractine forms are 170-370 ^ in maximum 

 diameter, and have rays 13-22 fi thick at the base. The diactine forms are 400- 

 900 fj. long, and 7-10 yu thick near the centre. Most of them are centrotyle. 

 The central tyle is not infrequently more than three times as stout as the adjacent 

 parts of the spicule. The single monactine form observed is 260 // long and 1 5 ^ 

 thick. 



The stalk-spicules (Plate 80, figs. 11, 12) bear spiral rows of proximally 

 directed spines on parts of their surface and terminate in anchors. The shaft 

 of the stalk-spicule represented (Plate 80, figs. 11, 12) is 39 /j. thick just above the 

 anchor, which is 145 ^ long and broad. 



The microhexactines (Plate 80, fig. 4) are 150-170 ju in diameter, and have 

 equal rays 3.5-4 m thick at the base. The rays are conical, fine-pointed, spined, 

 and nearly straight in their proximal part, but rather strongly curved towards 

 their ends. 



Of amphidiscs two kinds can be distinguished: — macramphidiscs and 

 micramphidiscs. 



The macramphidiscs (Plate 80, figs. 1, 2, 5-10) are 380-570 fj. long, most 

 frequently about 470 and 530 n. The shaft is straight, 20-25 ^ thick, and 

 thickened in or near the middle, only very slightly, or not at all, to a tyle, which 

 however is not clearly defined. This tyle may, when present, bear one or a few 

 blunt insignificant spines. The rest of the shaft is generally quite smooth. 

 The anchors are 120-228 m long, less than a third to nearly half of the whole 

 spicule, and 215-263 ^ broad. The proportion of their length to their breadth 

 is 100 to 115-191, on an average 100 : 147.8. The curvature of the anchor-teeth 

 decreases distally, and their end-parts generally diverge. The extreme tip of the 

 teeth, in the long anchors, is sometimes (Plate 80, fig. 2) bent inwards. The 

 teeth have smooth lateral margins, and are pointed at the end (Plate 80, fig. 10). 



The micramphidiscs (Plate 80, fig. 3) are 26-28 n long, and have terminal 

 anchors 9-10 n long, about a third of the whole spicule, and 8.5-11 n broad. 

 The proportion of anchor-length to anchor-breadth is 100 to 85-115, on an 

 average 100 : 102.5. 



Among the species of Amphidiscophora hitherto described, HyaJonema 

 martabanense F. E. Schulze ' appears to be the one most closely allied to the 

 fragment described above. This fragment differs from H. martaboncnsc by 



' F. E. Schulze. Hexactinelliden des Indischen Oceanes. III. Abh. Akad. Berlin, 1900, p. 12, t. 2. 

 Indian Triaxonia, 1902, p. 21, pi. 18. 



