YA MARINE BIOLOGY OF THE SUDANESE RED SEA. 
found between this and the largest specimens which measure anything up 
to4 mm. The diameter of the largest specimens at their thickest part varies 
from °15 to -18 mm. 
(6) Triradiates. 
(i.) Dermal (Text-fig. 8, c)—The triradiates of the dermal layer are of 
small dimensions and all markedly sagittal, with the paired rays two or three 
times as long as the basal. They form a sparse, but even covering, dermad 
to the oxea, over the whole of the external surface of the sponge, except in 
the immediate region of the oscular rim, where apparently they have not yet 
developed. The rays are all equal in diameter right up to their tips, which 
are rounded. The basal rays are straight, the apical curved. They are 
scattered over the surface without regard to orientation. 
Fig. 8.—Triradiates of Kebira uteordes, c and d X160, e X310. 
(ii.) Gastral (Text-fig. 8, d).—A thin gastral cortex is present between the 
flagellated chambers and the gastral cavity, in which there lies a layer of 
triradiates. These spicules are regular or slightly sagittal, but nearly all 
have the basal ray longer than the paired rays, in the sagittal specimens 
considerably so. All the rays are straight and cf the same diameter. The 
ends are rounded. 
