ON SOME JAPANESE CiVLCAREOUS SPONGES. 5 



pseudosagittal triradiates ; and 3) oxea which project nearly verti- 

 cally from dermal surface and which are grouped in small tufts 

 standing in no definite relation to radial chambers. 



The tubar skeleton near the osculum is of the inarticulate 

 type, consisting of the basal rays of subdermal pseudosagittal and 

 subgastral sagittal triradiates (PL II., fig. 11). In the remaining 

 parts of the sponge, where the wall is thicker and the chambers 

 are more elongate, the tul)ar skeleton receives an addition of some 

 rows of sagittal triradiates with outwardly directed basal rays and 

 is thus of the articulate type (PL II., fig. 10). 



The gastral skeleton is made up of tangentially placed tri- 

 radiates, of the paired rays of subgastral triradiates and of the 

 facial rays of gastral quadriradiates, of which the apical rays pro- 

 ject into the gastral cavity. 



The skeleton of the oscular margin is composed of oxea and 

 triradiates. The oxea I'lm longitudinally and parallel with one 

 îinother as well as with the downwardly directed basal rays of 

 the triradiates. 



Spicules. 



Dermal triradiates (textfig. 1, a, h). — Slightly sagittal. Basal 

 ray smooth, straight, ending in a sharp point, about 80 /^ long and 

 8 !'- thick. Paired rays longer and slightly thicker than basal ray, 

 not quite smooth, almost straight but sometimes slightly crooked, 

 gradually tapering and sharply pointed, about 120 ,« long and 10 /^ 

 thick. 



Subdermal triradiates (textfig. 1, c, d, e). — Pseudosagittal. 

 AU rays equally thick, lying nearly in the same plane. Basal ray 

 longer than paired rays, straight excepting slight curvature near 

 base, sometimes very slightly crooked, gradually tapering, sharp- 



