ADLOSACCUS MlTSUKURII. 123 



above markings, uot a few are comparatively short in proportion 

 to their breadth and present an elongate spindle-like shape. 

 These, like all other diactins of the species, are snbterminally 

 always rough-surfaced, and in some cases the roughness is seen 

 to extend nearly all over tlie rays in that some obsolete micro- 

 tubercles are found scattered even on the basal part. Such short 

 rough hypogastralia appear to lead over gradationally into the 

 gastralia Avhich may exceptionally be diactinie. The fact here 

 set forth indicates a close genetic relation between hexactinic 

 gastralia and underlying diactinie megasclene in general, and 

 seems to l)e noteworthy in view of certain Hexactinellids, as e. g. 

 Staurocalyplus pleorhaphides, in which the gastralia are repre- 

 sented, not by hexactins as in closely allied forms, but by diact- 

 ins alone. 



The dermalia (PI. X., fig. 9, 12) are rather thick-rayed 

 stauractins, the rays of which are in a plane slightly arched on 

 the outside. Occasionally pentactins with the unpaired ray 

 directed proximad and rarely tauactins are met with, but these 

 are certainly exceptional. Length of ray as measured from the 

 central point, 110-176 ii. Thickness at base, 13 // on an aver- 

 age. The rays slightly narrow outwards ; the tip is rounded or 

 somewhat conically pointed. Their surface is thickly beset all 

 over with unusually strongly developed, erect and conical prickles, 

 which constitute one of the most striking characteristics of the 

 species. The quadrate meshes formed by apposed rays of the 

 dermalia measure generally 100-130 ii in length of sides. 



The gastralia (PL X., figs. 10, 13) are strong and prickly 

 hexactins, for the most part fully twice as large as the dermalia or 



