VITROLLULA FERTILIS. 39 



thick in the middle of the body. The circular osculum at the 

 upper end measures 3 mm. in diameter. The contracted and 

 hiterally compressed base is attached to a horny worm-tube. 



The fourth specimen (Sei. Coll. Mus. Sp. No. 433) was ob- 

 tained by KuMA in November, 1895, from an unknown depth at 

 Inside Okinose. In shaj^e it is ovoid and slightly laterally com- 

 pressed. It is torn oif at the narrower end. Length, 14 mm.; 

 breadth, 7 h mm. Wall, about 2 mm. thick. The oval osculum 

 at the broader end measures 2h mm. I)v le mm. in diameter. 



All the specimens agree in having a smooth external surface. 

 Through the dermal layer, which is in close contact with the 

 choanosome, are seen the variously sized, ])ut generally small, 

 apertures to incurrent canals ; they rarely exceed f mm. in 

 width. The gastral surface presents a somewhat honeycombed 

 appearance owing to the fact that excurrent canals open freely 

 into the gastral cavity, the apertures being not covered over by a 

 continuous gastral layer (PI. III., figs. 7 and 8). Some of these 

 apertures may be li mm. wide. The gastral cavity is deep. 

 The body-wall gradually thins out towards the thin sim^ile oscular 

 edge. 



The texture of the sponge is delicate, soft and light. The 

 basal end, for a greater or less extent, is firm, which is due to 

 the basidictyonal mass being developed to a not inconsiderable 

 thickness. 



Spiculation. 



The parenchymalia consist of slender diactins and more or 

 less regular hexactins. 



The former are present in tolerable abundance, running 



