1908.] ON AFRICAN CALCAREOUS SPONGES. 449 



than the other paired ray. The basal ray is bent shai^ply near the 

 root ; but for this bend the point would project beyond the dermal 

 layer. A few spicules of a similar form are found lying tan- 

 gentially among the dermal triradiates. The subgastral triradiates 

 are alate, with equal paired rays and an oral angle of 155°. The 

 gastral skeleton (text-fig. 96) is a thick layer of alate triradiates 

 similar to those in the dermis, but slightly smaller and rather 

 more regularly placed. The oscule has no special skeleton. The 

 body-wall ends abruptly, and there is hardly a trace of a collar. 



Spictiles (text-Qg. 97), 



The triradiates are of four sorts : — 



(a) Alate triradiates from the dermis. Basal rays straight, 

 210-250 fji long x 10-12 /* thick. Paired rays straight, except for 

 a slight curvature near the junction of the basal ray, which 

 rounds the oral angle smoothly, 200 ^w, long x 8-10 /^ thick. Oral 

 angle 110°. \ 



(6) Alate triradiates from the gastral layer, similar to (a) but 

 smaller. Basal ray 180 yu, (occasionally much shorter). Paired 

 rays 140-150 /* long. Oral angle 115°-120°. 



(c) Subdermal triradiates. Basal ray (lying in the dermis) 

 straight, except for an angular bend near the root, 130-190/* 

 long X 14 />i thick. Centripetal paired ray straight, 240-420 yu, 

 long X 11-13 fjL thick. Dermal paired ray considerably bent near 

 the 'root, 160-190 /* long x 10-12 /i thick. Oral angle 100°. 



(d) Subgastral triradiates. Basal ray straight, 360-390 /a long 

 X 13-16 /I, thick. Paired rays, equal, bent downwards near the 



root, 1 80-240 fi long x 1 0-1 2 /* thick. Oral angle 155°. 



Grantessa zanzibaris, sp. n. (Text-figs. 98-102.) 



One specimen of this new species was dredged in 6-8 fathoms 



Text-fig. 98. 



G-rantessa sanziharis, sp. n. Nat. size. 



at Zanzibar. It consists of a mass of branching tubes of various 



29* 



