350 HYALONEMA (OONEMA) SEQUOIA. 



Besides these spicules which will be described below, a number of others, 

 chiefly amphidiscs (Plate 89, fig. 15e) and pinules, were found in the sponge. 

 Since, however, some of these kinds of spicules are very rare, and since the 

 other, more frequent ones are identical with spicules of Hyalonema (Hyalonema) 

 agassizi and Hyalonema (Prionema) fimbriatum trawled at the same Station 

 and contained in the same jar, I consider them as foreign. 



The superficial pinules (Plate 86, figs. 8, 13-26; Plate 87, figs. 1-7; Plate 

 88, figs. 7-13; Plate 89, fig. 15c) are nearly all pentactine, hexactine forms 

 being very rare. These pinules are very unequal in size, the largest attaining 

 quite unusual dimensions. The distal ray is straight and 0.18-1.4 mm. long, 

 most frequently about 0.9 mm. The length frequency-curve of the distal 

 pinule-rays is simple, with a single elevation at 0.9 mm., which shows that these 

 pinules form, in spite of their great dimensional differences, a simple, biometri- 

 cally harmonious group. The distal ray is 5.5-55 ii thick at the base, and 

 together with the spines is 19-160 m thick at the thickest -point. The maximum 

 thickness is two to four times as great as the basal thickness. The point of 

 maximum thickness lies rather far up, being usually three times as far from 

 the base as from the tip of the ray. The distal ray ends in a terminal cone free 

 from spines. This in the large pinules (Plate 87, figs. 3a, 5, 7; Plate 88, figs. 

 12a, 13a) is broad, rather blunt, and traversed by a remarkably thick axial 

 thread; in the smaller (Plate 88, figs. 7-10, 11a) it is either stout or slender, 

 and not infrequently sharp-pointed (Plate 88, fig. 10). In the large pinules 

 the distal ray is covered with spines quite down to its base (Plate 87, fig. 3b; 

 Plate 88, figs. 12b, 13b); in the smaller its basal part, for a short distance, is 

 quite smooth (Plate 88, figs. 7-10, lib). The length of this smooth basal zone 

 is, on the whole, in inverse proportion to the size of the spicule. The basal 

 spines of the distal rays of the large pinules are short, broad, conic, sharp-pointed, 

 and vertical. Distally they become more and more inclined towards the tip 

 of the ray. At the same time they increase in length up to the point of maxi- 

 mum thickness of the ray. From here up to the tip of the ray their length 

 remains about the same. In typical large pinules the basal spines are up to 

 7 ju long, and 10-14 ^ broad at the base. The upper spines are equally thick but 

 attain 35 m in length. Most of the inclined spines on the upper and middle- 

 parts of the ray extend longitudinally, in planes passing through the axis of 

 the distal ray. In a good many of the large pinules, however, irregularities 

 occur in the position of the spines. Either the spines on part of the ray are all 

 spirally twisted and directed obliquely to one side (Plate 87, fig. 2), or there is. 



