ON SOME JAPANESE C.\LCAREOUS SPONGES. 21 



The gastral cortex is thinner than the dermal and the ex- 

 halant canals are short. These spring each from a single or more 

 flagellate chambers. Diaphragm present at apopyle. Gastral 

 openings of exhalant canals are angular meshdike gaps, measuring 

 about 0.2 mm. across on an average. 



Skeleton (PI. TL., fig. 14). 



The dermal skeleton is fairly well-developed, being composed 

 of densely intercrossing rays of tangentially placed sagittal tri- 

 radiates and of the paired rays of subdermal pseudosagittal tri- 

 radiates. 



There is little regularity in the orientation of the dermal 

 triradiates, save in the tendency of their basal rays to take ab- 

 oscular direction. 



The tubar skeleton is typically inarticulate, being composed 

 of the centripetal basal rays of subdermal pseudosagittal triradiates 

 and of the centrifugal basal rays of subgastral sagittal triradiates. 



The gastral skeleton is more weakly developed than the 

 ilermal. It is made up of slender triradiates and quadriradiates, 

 l)oth tangentially placed but otherwise without definite orientation, 

 and of the strongly developed paired rays of subgastral sagittal 

 triradiates. 



Around the osculum are small oxea which are placed longi- 

 tudinally and parallel with one another. 



Spicules. 



Dermal triradiates (textfig. 4, a, b, c). — Slightly sagittal. Basal 

 ray is, as usual, shghtly longer and thicker than paired rays ; quite 

 straight, tapering from base gradually to a sharp point, 130-460 /^ 

 long and 20-48 /^ thick. Paired rays nearly equally long, slightly 



