BATHYDORUS LAEVIS SPINOSISSIMUS. 
101 
and their spinulation the triactine and diactine stauractine-derivates resemble 
the regular stauractines above described. 
The dermal spicules with more than four rays, which I am inclined to con- 
sider as stauractine-derivates with increased ray-number , are pentactines and 
hexactines. The pentactine forms (Plate 15 , fig. 20), which are met with rather 
frequently, have four fairly equal rays similar to those of the regular stauractines, 
and a fifth shorter ray vertical to the plane of the tips of the four others. The 
hexactine forms (Plate 15 , fig. 3) are very rare. They appear either as fairly 
regular hexactines with nearly equal rays, enclosing angles of 90° with their 
neighbours; or they are irregular, having rays unequal in length and irregular 
in position. These spicules are 100-200 m in diameter. In regard to the thick- 
ness of their rays and their spinulation they resemble the regular stauractines 
above described. 
The more or less pinule-like gastral hexactines (Plate 14 , fig. 12; Plate 15 , 
figs. 7, 8, 12-17 ; Plate 16 , figs. 9-11) have five quite similar and one differentiated 
ray, which latter corresponds to the distal ray of true pinules. This differen- 
tiated (distal) ray is straight (Plate 15 , figs. 12, 17; Plate 16 , figs. 9, 10); or, 
much more frequently, curved (Plate 15 , figs. 7, 8, 13-16; Plate 16 , fig. 11), its 
curvature often being very considerable (Plate 15 , figs. 8, 14, 16). It is at the 
base 2.5-6 u thick and, measured along its chord, 70-145 u. It is attenuated 
uniformly towards the end, or cylindrical in its proximal and conic in its distal 
part, or even slightly thickened near the middle, and always terminates in a fine 
point. It bears spines along the whole of its length. The spines are small, 
rather scarce, and nearly vertical on its basal part. Farther on they become 
more numerous, larger, and inclined towards the end of the ray. They attain 
their maximum length of 3-8 i± about half way up. Beyond this point the 
spines again become smaller, but retain their inclination towards the tip of the 
ray. The large spines are usually somewhat curved, concave towards the end 
of the ray. At its thickest (most bushy) point the distal ray is, together with the 
spines, 6-15 m in transverse diameter. In some of the gastral hexactines of 
specimen A the distal ray is stouter and more bushy than in the gastral hexac- 
tines of specimen B, where its basal thickness does not exceed 4.5 m, and its 
maximum transverse diameter, with the spines, 10 u- 
The four rays vertical to the differentiated one, which correspond to the 
four lateral rays of true pinules, are straight, usually rather abruptly pointed, 
43-94 /x long, and 3-6 n thick at the base. They are covered with spines 1.5- 
2.5 /x long, which either arise vertically, or are inclined towards the tip of the ray. 
