STAUROCALYPTUS GL ABER. 215 



the strands consist of tlie diactins only, and in still other places 

 these are seen to rnn singly, not being combined into bundles. 



The hijpogaHral strands are made up of similar diactins, and 

 of diactins onl3^ 



The dermaUa (PL XV., figs. 4-G) are almost exclusively 

 stauractins ; rarely pentactins and still more rarely tauactins or 

 diactins. The stauractins are very slightly convex on the out- 

 side. On some of them the atrophied proximal ray, and oc- 

 casionally also the distal, may 1)0 represented by a boss-like pro- 

 tuberance. Length of rays, 100-165 I' ; breadth at base, 6-9? n. 

 The rays may be said to be entirely rough; and it is a remark- 

 able fact that the microtubercles on their outer surface are 

 developed into more or less prominent, conical and vertically 

 erect spines. Those on the lateral sides of the rays are much 

 less strongly developed, while those on the inner side may be 

 said to be obsolete. The length attained by the spines on the 

 outer surface differs somewhat in different individuals, but at all 

 events their unusually strong development constitutes one of the 

 characteristics of the species. Even in a small specimen of only 

 6 mm. height, the spines in the position indicated are quite 

 prominent, though much thinner than in the larger specimens. 



The gaslraUa (Ph XV., fig. 7) are oxyhexactins of a moder- 

 ately large size. All the six rays in one spicule may sometimes 

 be of nearly equal length, but more frequently the free proximal 

 ray is the longest and the distal the shortest. Length of proximal 

 rays, 450-560 ji ; of ])aratangential rays, 330-352 /^ ; and of distal 

 rays, 190-262 /x Thickness at base, about 10/^ on an average. 

 The tapering rays belonging to one and the same spicule may 



