266 PERCY SLADEN TRUST EXPEDITION 



Previously known Distribution. Seychelles ( Wright) ; Samboangan (SoUas) ; Flinders 

 Passage, Torres Straits (SoUas) ; Red Sea (Keller, E.ow, Topsent) ; Okhamandal and Gulf 

 of Manaar (Dendy) ; ? South West Australia (Hentschel). 



Register Nos., Localities, &g. xlvii. 2 A, Praslin Reef; cxiii. 1 c, Egmont Reef; 

 cxx. 2 A, Salomon, 10 — 14 fathoms. 



22. Donatia stella-grandis n. sp. 

 (Plate 44, fig. 8 ; Plate 48, fig. 5.) 



The single specimen (Plate 44, fig. 8) is irregularly spherical, about 25 mm. in 

 diameter, attached at one (evidently the lower) side to a small mass of nuUipore. Part 

 of the surface is very distinctly tessellated, the flat polygonal tesserae being separated by 

 wide pore-grooves ; elsewhere the tesserae are obsolete and the pore-grooves hardly 

 discernible. There are two slight mammiform elevations on the upper surface, each of 

 which probably bears a small vent, now closed. The colour in spirit is dull greyish 

 yellow and the texture incompressible and of almost stony hardness. 



There is nothing peculiar to notice about the arrangement of the megascleres. They 

 radiate in stout, widely separated bundles from the interior of the sponge and penetrate 

 the cortex. On approaching the surface these bundles spread out into brushes of spicules 

 whose ends may project slightly beyond the surface. 



The cortex is only about 0'7 mm. thick, and cortex and choanosome alike are densely 

 packed with an almost solid mass of spherasters of various sizes. 



Spicules: — (l) Styli (Plate 48, fig. 5 a), tylostyli (fig. 5a') or strongyla (fig. 5a"); 

 measuring up to about 1'9 by 0*038 mm. These spicules are typically fusiform, but with 

 the centre of the spindle much nearer to the broad end. The broad end is never much 

 narrowed as compared with the middle of the shaft and is often distinctly tylote ; the 

 narrow end (centrifugal) may be sharply pointed or truncated. 



(2) Spherasters (fig. 5 h) ; rays elongated, conical, sharp, often slightly bent, 

 sometimes slightly and irregularly branched, about as long as the diameter of the 

 centrum ; total diameter very variable, up to about 0'25 mm. The branching of the 

 rays seems to be confined to the larger forms, which are very numerous. 



(3) Small chiasters (figs. 5 c, b d) \ with about 10 fairly stout, cylindrical rays, 

 usually slightly roughened towards the ends, which may appear slightly tylote or simply 

 strongylote ; total diameter up to about '01 6 mm. Abundant in cortex (especially at 

 the surface) and in choanosome. 



(4) Chiasters (fig. 5 c') of about the same size but with slender oxeote rays 

 (? roughened) ; these seem to occur in both choanosome and cortex but are not nearly 

 so common as the other chiasters, from which, however, they cannot be sharply separated. 



This species is distinguished from all the other species of Donatia known to me, with 

 the exception of Hentschel's Donatia tylota [1912], by the enormous size frequently 

 attained by the spherasters. The largest ones are about twice the diameter of those of 

 any other specimen in the collection, and six times the diameter of those of a specimen of 

 D. japonica from Praslin (R.N. XLIX.). Bowerbank speaks of the corresponding spicules 



