234 HYALONEMA (HYALONEMA) TYLOSTYLUM. 



The terminal- anchors are 34-85 m long, from less than a thii-d to more than 

 two fifths of the whole spicule, and 19-53 m broad. The proportion of their 

 length to their breadth is 100 to 46-88, on an average 100 : 58.3. As in the 

 large macramphidiscs, the relative breadth of the anchors is, roughly speaking, 

 in proportion to the size of the spicule. In the smaller small macramphidiscs, 

 under 170 ju in length, the proportion of anchor-length to anchor-breadth is 

 100 to 46-62, on an average 100 : 55.8; in the larger, over 170 ^ in length, 

 this proportion is 100 to 48-88, on an average 100 : 60.8. 



The individual teeth are curved strongly in their basal part. Distally the 

 curvature decreases, and it is on the whole such that the end-parts of the teeth 

 are usually slightly convergent. 



In one of the spicule-preparations I found an amphidisc ivith a supernu- 

 merary anchor-crowned ray arising from the central tyle. The main shaft is 

 110 /i long and 2 /x thick. The central tyle is 4 /x in diameter. The main ter- 

 minal anchors are 32 ^ long and 31 m broad. The supernumerary ray is 27 ^ 

 long. Its terminal anchor is 18 /x long and 28 ^ broad. The ends of adjacent 

 teeth of different anchors lie in a straight line. The main shaft and the super- 

 numerary ray are densely spined throughout. This spicule might be termed a 

 triadisc. 



The micramphidiscs (Plate 69, figs. 15-18) are 29-49 m long, most fre- 

 quently about 35 yu long. The shaft is straight, 0.7-1.1 yu thick, and either uni- 

 form in thickness, cylindrical throughout, or slightly and gradually thickened at 

 or near the middle to a central tyle which is sometimes 1.3 /u in diameter. The 

 shaft is either quite smooth or it bears a larger or smaller number of minute 

 spines. The anchors are 5-1 1 ^ loi^g, a quarter to a fifth of the whole spicule, 

 and 5-9 m broad. The proportion of their length to their breadth is 100 to 65- 

 150, on an average 100 : 88.9. The anchors of the largest micramphidiscs, that is 

 those over 40 m in length, are, on the whole, more slender than those of the 

 others. The proportion of anchor-length to anchor-breadth is in these large 

 micrainphidiscs 100 to 75-87, on an average 100 : 80.8. The individual anchor- 

 teeth are curved so that their end-parts are either parallel or convergent. 



The nearest allies of the sponges above described are the species Hyalonema 

 {Hyalonema) placuna and H. (H.) tenuifusum described in this Report. From 

 these they differ by possessing tylostyle megascleres; by being destitute of 

 microhexactines with two longer opposite (apical) and four more or less reduced 

 (lateral) rays; by the smaller size of the distal rays of their dermal pinules, and 

 by other characters. 



