DENDY— HOMOSCLEROPHORA AND ASTROTETRAXONIDA 265 



from that species in the structure of the cortex. I refrain at present from expressing any 

 opinion as to the supposed identity of D. rohusta and D. cliftoni [Bowerbank 1873 a] 

 with this species. 



Previously , known Distribution. S.W. AustraHa (Bowerbank, Hentschel) ; Bass Str., 

 Port Jackson (SoUas) ; Queensland (Berhn Museum ; a section in my possession labelled 

 Tethya Jissurata Ldf and numbered 1120); ?Java Sea and Gaspar Strait (Lindgren) ; 

 Ceylon (Dendy). 



Register Nos., Localities, &c. xlvii. 2 b, c, d, f, Praslin Reef; Lii. 8 a, b, liv. 1, 

 2 A, c, D, all from Coetivy ; ex. 7, cxi. 4, 5, cxiii. 1 a, b, all from Egmont Reef; cxix. 

 10 A, B, Salomon. 



21. Donatia seychellensis (Wright). 

 (Plate 48, fig. 4.) 



Alemo seychellensis Wright [1881], 



Tethya seychellensis Sollas [1888]. 



Tethya seychellensis Keller [1891]. 



Tethya seychellensis Topsent [1893 b]. 



Tethya ingalli (pars) Lindgren [1898]. 



Tethya seychellensis Kirkpatrick [1900 a]. 



Tethya lyncurium var. c. Dendy [1905]. 



Donatia Ingalli Topsent [1906 b]. 



% Donatia Ingalli (pars) Hentschel [1909]. 



Tethya seychellensis Row [1911.] , 



Donatia seychellensis Dendy [1915]. 



This species is characterised above all by the large choanosomal oxyasters (Plate 48, 

 fig. 4 d), usually with six, often branched rays. The hexradiate character of these spicules 

 has already been pointed out by more than one writer and seems to be fairly constant. 

 In the " Sealark " specimens the cortical and choanosomal tylasters (fig. 4 c, d') are also 

 typically hexradiate. The measurements of the three kinds of aster in the "Sealark" 

 specimens are as follows : — Large spheraster (fig. 4 a), when fully grown, 0'07 mm. ; 

 cortical tylaster 0'012 mm. ; choanosomal oxyaster (total diameter) 0'04 mm. 



The three specimens in the collection have the usual subspherical form and more 

 or less strongly tessellated surface, and all of them, in parts, show remarkably wide 

 gaps (pore-grooves) between the tesserae. The largest is about 25 mm. in diameter. 

 The colour in spirit is grey or yellowish. One specimen only shows a few elongated, 

 slender conuli (? budding). 



In all three the cortex is very lacunar and does not contain nearly so many 

 spherasters as in the specimens of D. ingalli, while beneath the cortex and between the 

 radiating spicule bundles (which pierce the cortex and spread out as usual) are found 

 numerous loose, radially arranged styli, as in D. japonica. 



The large red Donatia so common in the neighbourhood of Port Phillip, Victoria, 

 possesses large oxyasters very similar to those of D. seychellensis, but I am inclined to 

 think, on account of other characters, that it is specifically distinct both from D. seychel- 

 lensis and D. ingalli. 



SECOND SERIES— ZOOLOGY, VOL. XVIL 34 



