STAUROCALYPTUS TUßÜLOSÜS. 179 



the derinalia. In all these the rays taper slightly towards the 

 rounded or obtusely pointed ends. Their length as measured 

 from the spicular center, 84-190//.; on the average about 14.0 n. 

 Breadth of rays near base, 7-12 ^. I have noticed that the 

 stauractins attain on the average a considerably larger size than 

 the pentactins (see Contrib. III., PL YI., fig. 12). (For the sake 

 of comparison I may mention that in /V. doivlingi the dermaliii 

 are known to be <»;enerallv pentactins and occasionally diactins. 

 Length of rays, lGO-180/^; according to Lambe, 160/^- on the 

 average). 



The (/aslralla are all hexactins with rays similar in appearance 

 to those of the dermalia. Length of I'ays, 130-200/^ (in >S. 

 dowUng'i, 80-100//). 



Oxyhexaders (Contrib. III., PI. VI., fig. 17) occur in abun- 

 dance. They are mostly normally developed ; less frequently are 

 they hemihexactinose. Quite hexactinose forms are very rare. 

 The central node is often swollen to a spherical shape. The 

 principals are as usual short — often exceedingly short. The dia- 

 meter is in general 75-115;^ (in S. dowlirtgl 100-120 /i). 



The oxyhexasters in the subdermal region mostly measure 

 less than 100 y- in diameter. In them the terminals are slender, 

 slightly rough and 2 or o in number to each principal. 



Those situated more deeply in the wall are on the whole 

 somewhat larger, many also having perceptibly stronger terminals, 

 which are then nearly smooth-surfaced. 



From this species again I am in a position to record a case 

 of an oxyhexaster in which five of the principals bore each a set 

 of two, nearly equally developed terminals, but the sixth principal 



