ON SOME JAPANESE CALCAEEOUS SPONGES. 29 



cd at their free end with a circular oscnlam of J-1 J mm. dia- 

 meter ; the marginal fi-ingo is scarcely visible to the naked eye. 

 The tubes attain a breadth of about 5 mm. ; thickness of wall 

 about 1 mm. The colour of the sponge in the preserved state is 

 brownish white. 



The following description is based on the type- specimen. 



Canal system (PL IL, fig. IG). 



The canal system of this species is not of tlie true syconoid 

 type, unlike others of the genus. It is rather of an intermediate 

 type between the sylleibid and the leuconoid. 



The flagellate chambers vary much in shape and size, fi'om 

 those of spherical shape measuring 50-100 i>- diameter to others of 

 an elongate sac-like configuration, say, 200 /^ by 80 /^ in dimension. 

 They are closely set in the chamber layer, showing a somewhat 

 radial— though not quite strictly radial — arrangement around wide 

 and long, sometimes slightly branched exhalant canals. The posi- 

 tion of nucleus in the collar cells is apical. 



The exhalant canals perforate the thin gastral cortex and 

 open into the gastral cavity by angular mesh-like pores of various 

 sizes, up to 150-250/^ in length. 



Skeleton (PI. H., fig. 16). 



The fairly thick dermal skeleton consists of : 1) small sagittal 

 triradiates, lying tangentially in several layers, with their basal 

 rays generally directed towards sponge base ; 2) large oxea run- 

 ning longitudinally ; and 3) the paired rays of subdermal pseudo- 

 sagittal triradiates. Besides these, there may occur slender hair- 

 like oxea, very sparsely distributed and projecting on the dermal 

 surface. 



