AULOSAOCÜS MITSUKURII. 117 



ing between 95 /^ aud 475 // in the same rosette. I thought it 

 possible that the terminals formed six bunches corresponding to 

 the six original principals and that in each Inmch the longer 

 terminals occupied a more central position than the shorter ; but 

 this could not be verified. On the coutrary, those of different 

 lengths seemed to be situated together promiscuously. 



The terminal disc (PI. IX., fig. 9) is somewhat conically 

 convex on the outer side. It measures about 10 // in diameter. 

 The margin shows a row of numerous small teeth. 



The ridcrodiscohexaster (PI. IX., fig. 10) of a very dehcate 

 nature is common in the choanosome as well as iu the endosome. 

 In some places in the former it occurs almost as numerously as 

 the oxyhexaster. Diameter, 26-38 /^. 



The shape is spherical, the minute granule-like terminal discs 

 however do not lie on an even level at the surface. The termi- 

 nals are so exceedingly fiue that they can scarcely l)e perceived 

 unless a very high power of the microscope be used for the ob- 

 servation. The princi[)als are slender and form a cross measur- 

 ing about 7h fi in axial length. Tlieir outer ends do not show 

 a disc-like expansion, nor is the central node spherically swollen. 



AULOSACCUS MITSUKURII Ij. 



PI. X., figs. 1-15. 



Aulosaccus onitsukurii, Ijima, '98, p. 52. 



A single specimen belonging to the Sei. Coll. Museum formed 

 the type of this species at the time it was first described by me 



