530 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 54. 



cavity; they are more or less united at places where they come into 

 contact with one another. 



The articulate tubar skeleton is composed of triradiates, its proxi- 

 mal joints being formed by the basal rays of subgastral triradiates. 

 Those tuber triradiates which form the distal joints have the basal 

 rays grouped into tufts together with a number of oxea. The gastral 

 skeleton is made up of triradiates, quadriradiates, and the paired rays 

 of subgastral triradiates. The two former are fairly regularly ar- 

 ranged around gastral apertures with basal rays directed downward 

 and with apical rays projecting into the gastral cavity. The quadri- 

 radiates are much less numerous than the triradiates. The oscular 

 margin is very thin, but richly supplied with spicules; externally 



Fig. 2. — Stcon simushirbnsis. a, tcbar triradiates. b, subgastral triradiates. 



C, gastral triradiates. d, GASTRAL QUADRIRADIATES. 6, TRIRADIATE OF OSCULAB 

 MARGIN. f, QUADRIRADIATE OF OSCULAR MARGIN. g, OXEA OF OSCULAR MARGIN. AU 



X150. 



there are found triradiates, large oxea, and linear spicules, all which 

 form a thin fringe, and internally there exist quadriradiates in a 

 layer. Both the tri- and the quadriradiates lie tangentially with 

 downwardly directed basal rays. 



Spicules. — Tubar triradiates (a) slightly sagittal with slender rays. 

 Basal ray longer and slightly thinner than paired rays, tapering 

 from base to sharp point, straight, 100-140^1. long and 6[x thick at 

 base. Paired rays slightly doubly curved forewards in basal parts 

 and backwards in the remaining parts ; 90-100[x long and 8\i thick at 

 base. Subgastral triradiates (&) sagittal. All rays slender, taper- 

 ing from base to sharp point, not lying in the same plane. Basal 

 ray distinctly longer than paired rays, straight, about 200[jl long and 

 6-8(x thick at base. Paired rays strongly diverging, distinctly curved 



