AULOSACCÜS MITSUKURII. 125 



appreciable difference in appearance between those in the peri- 

 phery and others situated more deeply in the wall. Forms like 

 those depicted in PL X., figs. 4-6, predominate. From each 

 exceedingly short principal thei'e diverge 2 or 3, seldom 4, rather 

 thin, obsoletely rough-surfaced and nearly straight terminals. 

 The microtubercles on the basal parts of these frequently have 

 the distinct appearance of l^eing retro veited. Occasionally the 

 oxyhexaster is hemihexactinose (fig. 7) ; i. e., while one or more 

 of the six principals bear each two terminals, the rest are uni- 

 terminal, in which latter case the entire ray is either straight or 

 else is bent at the base. The quite hexactinose oxyhexaster 

 occurs but very rarely ; only one or two instances of it being all 

 that I have encountered. 



The /nacrodiscohexaster (PI. X., figs. 2 & o) is much smaller 

 than that of either A. schuhet or A. ij'uiiai, a fact which at 

 first made me hesitate somewhat to refer the present species to 

 the same genus ; but on furtlier consideration I can but think 

 that its generic separation on account of that difference alone can 

 scarcely be justified. 



The macrodiscohexaster may be said to be spherical in shape. 

 It measures 80-120 //. in diameter, being therefore of about the 

 same size as average oxyhexasters of the species or somewhat 

 smaller. It is tolerably rich in the number of terminals, which 

 are not quite thin and are generally straight and nearly uniformly 

 thick throughout their length. Not less than ö terminals arise, 

 not in a circle but promiscuously, from the swollen knob-like end 

 of each very short principal. The terminal discs are small ; they 

 are furnished with minute marginal teeth, six or more to each. 



