R. OKINOSEATsA. — SPICULATION. 233 



with the solid substratum. Here the meshes are not wider than 

 the beams themselves. The irregular cribellate plate thus formed 

 was known to F. E. Schulze ('87, p. 3S ; pi. LXiv, fig. 3) from 

 Bhahdocalyptus inoUh, etc. 



Spicules whicli might correspond to the o^cularia of Euplec- 

 tclla were not noticed in any of the specimens, except in a rather 

 small individual from Okinosé (Sc. Coll. Mus. No. 490). In 

 this, the iris-like membrane of parietal oscula (PI. VIII, fig. 37) 

 was supplied with an abundance of small spinose hexactins, most 

 of which differed from ordinär}^ microxyhexactins in having 

 somewhat thicker rays terminating in rounded ends, and also in 

 frequently having one or more of the rays reduced in length. 

 Thus, they were not uncommonly pentactins, and occasionally 

 even diactins, in all of which the suppressed rays were re- 

 presented by knobs or rudiments of variable length. The 

 presence of transitional forms, however, clearly indicated their 

 derivation from microxyhexactins by modification. They are 

 evidently a sort of spicules which is of inconstant occurrence 

 in the species. 



The dermalia (PI. YIII, figs. 14-18) are hexactins of vari- 

 able size and strength. jMany of them may be said to be sword- 

 shaped with the proximal ray more than twice as long as the 

 paratangential rays ; while others, especially those of weak 

 development, may have that ray of nearly equal length, or 

 even somewhat shorter than these. The distal ray is always 

 distinguishable b}^ its comparative shortness, by its rounded or 

 conical end, and by the relatively more numerous and more 

 pronounced development of the microtubercles on its surface. 



