228 HYALONEMA (HYALONEMA) TENUIFUSUM. 



more rarely, slightly inclined, and measure 5-12 ix long and 2-4 m thick. From 

 the other parts of the shaft arise a greater or smaller number of low truncate 

 or terminally rounded protuberances 1-2 ix long and 2-3 yu thick. The terminal 

 anchors are 66-110 ;u, about a third of the whole spicule, and 61-97 ix broad. 

 The proportion of their length to their breadth is 100 : 84 to 102, on an average 

 100 : 93.6. The anchors in the larger forms are relatively broader than in the 

 smaller, the fraction i^^ being, roughly speaking, in proportion to the length 

 of the amphidisc. The anchor-teeth arise vertically from the shaft, and are 

 curved concave towards it. This curvature decreases distally, and is on the 

 whole such that the ends of the teeth couA-erge more or less. When this conver- 

 gence is great the anchor may be, at its end, as much as 10 n narrower than in its 

 broadest part. The individual teeth are 10-15 fi broad, and abruptly and not 

 sharply pointed (Plate 67, figs. 3, 4; Plate 68, fig. 1). 



In specimen {h) the large macramphidiscs are similar but ha\^e narrower 

 anchors. Their dimensions in this specimen are : — length 202-340 n ; thickness 

 of shaft 5-13 yu; diameter of central tyle 8-22 /x; length of anchors 46-114 /j; 

 breadth of anchors 43-98 /j; proportion of anchor-length to -breadth 100 : 65 to 

 98, on an average 100 : 80.8. 



The small macramphidiscs (Plate 67, figs. 13, 14, 22-25; Plate 68, figs. 22, 

 23) are in specimen (a) 129-160 n long, in ih) shorter, only 77-152 ix long. The 

 shaft is straight or, rarely, curved and 2-3 yu thick. A cluster of irregularly dis- 

 posed, more or less oblique, and often considerably curved, cylindrical, truncate 

 spines with a maximum length of 3 ^ arises from a point in or near the middle 

 of the shaft. At this point the shaft is usually, but by no means always, gradu- 

 ally thickened to a tyle sometimes 6 ix in diameter. The remaining parts of the 

 shaft are quite densely covered with smaller spines, generally cylindroconical 

 and truncate, which have a maximum length of 2.3 m and are 1 yu thick. The 

 terminal anchors are somewhat different in the two specimens. In (a) they are 

 36-54 /n long, over one quarter to over two fifths of the whole spicule, and 22-30 yu 

 broad, the proportion of their length to their breadth being 100 to 48-64, on an 

 average 100 : 58.5; in {h) they are 34-63 m long and 18-43 m broad, the propor- 

 tion of their length to their breadth being 100 to 46-75, on an a\'erage 100 : 54. 

 Relative to the length of the whole spicule these anchors in specimen (o) are 

 considerably shorter than in (b). The proportion of the total length of the 

 spicule to the anchor-length is in (a) 100 : 27 to 34, on an average 100 : 30.5; in 

 (To) 100 : 34 to 44, on an average 100 : 38.8. The individual anchor-teeth are 

 strongly curved, concave to the shaft at the base, and only slightly and rather 



