262 I. IJIMA : HEXACTINELLIDA. I. 



sword-like, at places where the dermal layer touches the parenchy- 

 mal mass, into which the ray in question enters like a nail. 



The dermalia are seen to extend over the membranous zone 

 around the parietal osciila, forming the usual latticework right 

 to the edge. Many of them in this situation have a very short 

 proxim.al ray. In passing it may be mentioned that no more 

 specially differentiated oscularia were found in this than in other 

 species of the genus. 



A much larger size as given above is attained by some — 

 not all — sword-like dermalia on the cuff-edge as well as on the 

 summits of parietal prominences, in intermixture with the pros- 

 talia occurring in these places (PL X, fig. 11). With the general 

 growth in size of the entire spicule, the free distal ray especially 

 undergoes elongation and development. It assumes a slender 

 spindle-like shape, while the surface for nearly its entire length 

 becomes roughened by the presence of microtubercles (Pi. X, fig. 

 18). I have measured such distal rays of 300 n, 400 /-«, 500 <« and 

 more in length with a breadth of 22 ij. and over at the thickest 

 part. Thus, as before said, the dermalia approaches, and finally 

 becomes indistinguishable from, the smaller prostal hexactins. 



The gastralia, found in irregularly scattered distribution, are 

 pentactins of moderate size, with the atrophied sixth ray indi- 

 cated by a gentle swelling- The rays are straight or nearly 

 straight, slightly tapering or uniformly thick (12 // or less) 

 throughout. End almost always rounded ; subterminally obsoletely 

 rough. The paratangential mys are often of unequal length in 

 the same spicule; length up to 700/^. They run not always 

 along the extreme gastral surface, being sometimes overlaid by 



