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446 ON AFRICAN CALCAREOUS SPONGES. [May 12. 



The triracliates are of two sorts : — 



(6) Slender dermal triradiates, subregular. Rays 160-280 /a 

 long X 5-10//, thick. 



(c) Subregular triradiates from the body. Basal ray straight, 

 120-400 /A long X 20-32 /x, thick. Paired rays almost straight, 

 140-550 ^l long x 16-26 /a thick. 



The quadriradiates are of two sorts : — 



(fZ) Subregular quadriradiates lining the excurrent canals. — 

 Basal rays straight, 180-250 /a long x 10-20 fx. thick. Paired rays 

 nearly straight, 200-280 jx long x 6-17 /t thick. Oral angle 120°. 

 Apical rays 170 x 6-8 yu. thick. 



(e) Alate qviadriradiates from the gastral skeleton, similar 

 to (d) but with a larger oi'al angle, about 135°. Apical ray 

 50 fx long x 6-8 fx thick. 



Grantessa simplex, sp. n. (Text-figs. 93-97.) 



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

 at Wasin, and one specimen was collected on the shore of Chwaka 

 Bay, Zanzibar. 



They both consist of a confused mass of anastomosing tubes 

 (see text-fig. 93). The oscules are at the free ends. The tubes, 

 as preserved, are a good deal flattened and vary in size from 

 2-5 mm. in diameter. Both external and internal surfaces are 

 smooth. 



Text-fiff. 93. 



Grantessa simplex, sp. n. Nat. size. 



The structure of the body- wall is very regular and typical of 

 the genus Grantessa (see text-fig. 94). 



The skeleton is formed entirely of triradiates. The dermal 

 skeleton (text-fig. 95) consists of alate triradiates lying tangen- 

 tially, without orientation. The subdermal triradiates (c, text- 

 fig. 97) are modified dermal spicules ; the centripetal ray'is one 

 of the paired rays, not the basal ray*; it is considerably longer 



* Cf. Polejaeff (2). 



