K. OKIXOSEAXA. — SPICULATIOIT. 231 



light up to the pointed end, phicing it beyond the reacli of doubt 

 that we have here to do with a true hexactin. Spicules of 

 simihar or exactly the same appearance are known from Ta'geria 

 as well as from Walteria. 



The microxyhexactins are present in all parts of the paren- 

 chyma. They seem to be more abundant iu the inner than in 

 the outer trabecular layer. The}' mostly occur loosely, sometimes 

 tightly clasped in the bundles of parenchymal diactins. Further, 

 I have seen tliem situated and arranged after the manner of 

 canalaria in places in the excurrent canals. 



In the deeper parts of the parietes I have occasionally met 

 with isolated spicules, which somewhat differed from, but seemed 

 to integrade with, the microxyhexactins. We here have to deal 

 with rather small pentactins or hexactins or such hexactius as 

 ajiproach a pentactin by the reduction to a greater or less extent 

 of one of the rays (PI. VIIT, figs, 27, 28, 33). The rays differ from 

 those of microxyhexactins in being somewhat thicker and less 

 tapering, in having rounded or bluntly pointed ends and in being 

 sparingly supplied with prickles only near the end. The prickles, 

 however, have sometimes been found to extend nearly all over the 

 rays, though in a weak state of development. I am inclined to 

 regard these spicules as repi'esenting parenchymal microxyhexac- 

 tins in the way of differentiation towards gastralia or canalaria. 



The hard basal mass consists of a rigid, close and irregu- 

 larly meshed framevYork of siliceous beams, which bear on their 

 surface sparingly and unevenly distributed microtabcrcles. The 

 beams arise by extensive synapticular fusion of all the paren- 

 chynialia in this region, except the intermedial microxyhexactins, 

 which, together with the hexasters, usually remain free in the 



