The Sponges of Lake Biwa. 



the diagnosis of S. dementis was based, while Phase III is not far 

 removed from those that formed the type of S. yunnanensis — so far 

 as external characters are concerned, — but the supposed differences 

 in the skeleton and the spicules are, as will be clear from what we 

 have already said, by no means diagnostic of any one phase or 

 variety. 



S. dementis was described from Luzon in the Philippine 

 Islands, while the type of S. yunnanensis were from Lake Tali-Hu 

 in Yunnan, China. Otherwise the species is only known from 

 Lake Biwa, in which it is abundant in situations not exposed to 

 dessication, and from the settling-tanks of the Kyoto water- 

 works, which are supplied from the lake. 



Subgenus Eunapius, Gray. 



The air-spaces on the gemmules of this subgenus have a very 

 regular form and arrangement. They are relatively large, 

 polygonal in cross-section and arranged in numerous concentric 

 layers. The gemmule-spicules are as a rule more or less horizontal. 

 The only species of this subgenus found in Japan is almost cosmo- 

 politan. 



Spoiigitfa fraffilis LeiDY. 



PL I, fig. 9. 



1909, Annandale Annot. Zool. Japon. VII, P. 106, PI. II, fig. 1. 



The external appearance of this species is usually character- 

 istic, for it forms flat layers or crusts without branches or con- 

 spicuous protuberances and has numerous small oscula, each of which 

 is surrounded by a star-like figure produced by the main exhalant 

 canals running superficially in a horizontal direction to the orifice. 

 The colour is usually brown. 



The skeleton is more compact than in S. lacustris. The 

 skeleton-spicules are smooth, fairly slender and sharply pointed. 

 There are no free microscleres. The gemmule-spicules are some- 

 what variable in form and may be either cylindrical or spindle- 

 shaped in outline. They are always slender and relatively long 

 and covered with short irregular spines. 



