DENDY— HOMOSCLEROPHORA AND ASTROTETRAXONIDA 263 



rangfe of variation from strongly tessellated in polygonal areas to conulose and proliferous. 

 Although the varying character of the surface causes the specimens to differ very 

 strikingly in external appearance I do not think that it implies any specific or even 

 varietal distinction, but merely phases of growth, possibly associated vrith a periodic 

 activity in throwing off buds *. None of the specimens exceed a diameter of about 

 20 mm. The colour in spirit is light grey or yellowish. 



The cortex is only about I'O mm. thick, with more or less well developed intra- 

 cortical crypts from which narrow inhalant canals run into the choanosome. 



The spicule-bundles of the main skeleton penetrate the cortex and either spread out 

 in brushes at the surface (in the tesserse) or are continued into well-marked conuli. 

 In the outer pai't of the choanosome, between the spicule-bundles, numerous loose 

 megascleres (styli or subtylostyli) are radially arranged. These cease abruptly just 

 beneath the cortex. 



The large spherasters are rather sparsely scattered in the cortex. In the choanosome 

 their numbers vary greatly and they are apt to be mixed with small forms that probably 

 represent, in part at any rate, developmental stages. 



The small tylasters form a distinct dermal layer, as well as occurring scattered in cortex 

 and choanosome. 



The spherasters (Plate 48, figs. 2 a, 2 b), when fully grown, range from about 0*04 to 

 about 0'07 mm. in total diameter. They have sharp conical rays whose length is about 

 half the diameter of the large centrum. 



The cortical and choanosomal tylasters (fig. 2c, 2d) closely resemble one another 

 both in form and size and range from about 0'0082 to 0"0164 mm. in total diameter. 

 They usually have more than six rays, but in R.N. xlvii. 2 E they are usually six-rayed. 



The chief distinguishing features of this species are the tylote character of the cortical 

 and choanosomal chiasters, the absence of oxyasters and the comparative scarcity of 

 spherasters in the cortex. The choanosomal chiasters may, however, occasionally lose the 

 heads of the rays and exhibit a transition to those of D. ingalli (fig. 2 e). 



I pointed out in my Report on the Ceylon sponges that the tylote character of the 

 chiaster may occasionally occur even in a British Donatia, and I must now add that Deszo, 

 as far back as 1878, figured typical tylasters for a specimen of Donatia from Naples, 

 identified by him as Tetliya lyncurium. Perhaps he really had D. japonica before him. 



Previously known Distribution. Manila (SoUas) ; Java Seas (Lindgren) ; Ceylon 

 (Dendy) ; Zanzibar (Baer) ; Red Sea (Topsent, Row); ? Naples (Deszo). (For other 

 possible localities vide Lindgren [1898] and Hentschel [1909].) 



Register Nos., Localities, &c. xlvii. 2 E, xlvii. 3, XLix., all from Praslin Reef; 

 Liv. 2 B, Coetivy ; LVii. 10 A, B, Coin, Peros ; LXii., Lagoon, Diego Garcia, 8.7.05 ; cvii. 

 2, Amirante, 14.10.05, E. 17, 12 — 18 fathoms ; cxx. 2 b, Salomon, 10 — 14 fathoms. 



* Compare SoUas's remarks on this subject in the case of Donatia seychellensis [1888]. 



