170 ART. 7. 1. IJIMA : HEXACTINELLIDA, IV. 



to mention the occasional diactins above referred to. In all the 

 different forms it is quite usual that the suppressed ray or rays 

 are indicated by vestigial knobs. Such rays as are well developed 

 are 100-165 !>■ long and (> /< or less broad at base ; the micro- 

 tubercles on their surface are sparse and weakly developed ; their 

 tips nre conically pointed. Not only are the rays considerably 

 more slender tlian in the corresponding spicules of all other 

 closely I'elated species of the genns, but also the roughness of 

 surface is far less prononnced, as has already been pointed out 

 by F. E. Schulze. 



The (jadralia (PI. XIV,, fig. 32) are oxyhexactins with 

 similarly characterized rays, which measure 100-220 1'- in length 

 and not over 5 /< in breadth at base. Over the interspace between 

 the freely open excurrent canalar apertures, the gastralia are 

 present in abundance, forming a nearly regularly quadrate-meshed 

 latticework. In this, the laths are formed frequently by two or 

 more gastral paratangentials combined in a loose strand. 



The oxyhexasters (PI. XIV., figs. 27, 28) are small and 

 very slender-rayed. Diameter, 88-130 /<. Those situated in the 

 periphery of the wall are on the whole somewhat smaller than 

 others in deeper situations. The short, often exceedingly short, 

 principals bear each 2-3, nearly straight or slightly wavy and 

 obsoletely rough terminals. Less frequently there is only a single 

 terminal to one or more principals in an otherwise normal oxy- 

 hexaster (hemihexactinose). In the preparations at my disposal 

 I have not discovered any regularly hexactinose oxyhexasters, but 

 I presume that the spicules spoken of by F. E. Schulze as 

 " small, weakly developed oxyhexacts " (Call. Rep., PI. LXV., 



