98 ART. 7. — T. IJIMA : HEXACTINELLIDA, IV. 



seiited by only the central parts. The size is small, measuring 

 only 46-50 p. in diameter. The general form can not be said 

 to be spherical, since the terminals to each principal form a dis- 

 tinctly separate tuft shaped like the perianth of a lily. The six 

 principals arising from the small and spherical central node are 

 short ; the measurement from end to end of two principals in 

 one axis is scarcely 10 //.. Their outer ends do not appear to be 

 expanded. The thin terminals (20 /^ long), of which there are 

 10, 12 or more in a tuft at the end of each principal, are of 

 the most delicate description. They thicken just perceptibly to- 

 wards the outer end which terminates in a minute pinhead-like 

 disc. The entire ray, with the outwardly expanding tuft of ter- 

 minals, is in appearance not unlike that of the octaster of certain 

 Acanthascin?e. 



The above discohexaster as compared with that of H. saganii- 

 ensis presents marked differences. (Compare text-figure 4 [magn. 

 500 times] with PI. VIL, fig. 5 [magn. 300 times]). It is con- 

 siderably smaller (46-50 /i dia. against 80-90 // dia.), and the 

 fact that ^ the much more numerous terminals are arranged in 

 distinct tufts gives to the spicule a very characteristic appearance. 

 I think the différences indicated are of sufficient import to justify 

 the specific separation of IL similis from the foregoing species.* 



" Too late to admit of introducins; change?; in tlie text I iind that the discoliexaster 

 liere described is not the only kind but that there is to be ascribed to the species another 

 which I had entirely overlooked. Having occasion to re-examine the preparations, I have 

 come across a discohexaster lying near tlie gastral surface, which closely resembles thai of 

 H. sa'jamienÙH (PI. VII., fig. 5). Spherical in shape, with diameter of 76 [;.. Terminals, :! 

 or 4 to each short and minute principal; exceedingly fine and very slightly thickened to- 

 wards the outer end which terminates in a minute disc. Having once seen it, I have suc- 

 ceeded after a prolonged search on several preparations in discovering a few more of tlie 

 same kind. It mu-t be said that this discohexaster is of very rare occurrence; possibly it 

 is on the verge of disajipearance. But then it seems undeniable that we have in it a dis- 

 cohexaster form which is common to both H. sagamiensis and //. similis. Was not the 

 smaller form (text-fig. 4), considered in the text to be peculiar to the latter species, over- 



