CHAUNOPLECTELLA CAVERNOSA. 65 



proxiraad and the rest run paratangentially, or all the four rays 

 alike may support the dermal memhrane in that the t\YO unpaired 

 rays are forced apart from each other so as to form an angle of 

 more than 90° between them. — Triactinic dermalia are most 

 generally in the form of tauactins. Seldom was the form represent- 

 ed by three half-axes met with. Except that a ray is never 

 directed distad, the triactins may lie in all sorts of positions as 

 regards the directions of the rays. — Diactinic elements of the 

 dermal spicules are of the uniaxial form. They are always slender 

 and comitalia-like, occurring but occasionally as components of 

 spicular bundles in the dermal layer. — Altogether the dermalia are 

 irregular in shape and the latticework formed by them is likewise 

 irregular in appearance. 



The gastral layer closely resembles the dermal in its spicular 

 structure, except in the fact that hexactins with a freely projecting 

 proximal ray are here of somewhat common occurrence. In the 

 smaller specimens of the species, the hexactinic gastralia are 

 below the medium size and have all the rays nearly equally long; 

 they are comparable in all respects to the canalar oxyhexactins 

 soon to be described. In the larger individuals, the same spicules 

 are much larger, being about as large as the dermalia in the 

 same specimen, and have rays of unequal length. The free 

 proximal ray is always much shorter than most others in the 

 same spicule. 



Oxyhexactinic canalaria of rather small size line the walls 

 of both incurrent and excurrent canals in irregular distribution 

 (PI. IV., fig. 8; PI. v., fig. 12). They are nearly regular in 

 shape and measure 200 /-< and upward (mostly about 500 /^-) in 



