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 ij. 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 n thick and, measured along its chord, 70-145 n. It is attenuated 

 uniformly towards the end, or cyhndrical in its proximal and conic in its distal 

 part, or even sUghtly 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 maximmii length of 3-8 m about half way up. Beyond this point the 

 spines again become smaller, but retain their incUnation 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 ^ 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 n, and its 

 maximmn transverse diameter, with the spines, 10 /x. 



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 n long, and 3-6 m thick at the base. They are covered with spines 1.5- 

 2.5 n long, which either arise vertically, or are incUned towards the tip of the ray. 



