DENDY— HOMOSCLEROPHORA AND ASTROTETRAXONIDA 251 



The choanosome contains numerous large, oval, thin-walled, vesicular pigment-cells, 

 about 0"04 mm. in longer diameter and containing a granular reticulum of brown or yellow 

 pigment to which the colour of the sponge seems to be chiefly due. 



This is an extraordinarily interesting species, evidently closely related to Aurora 

 [Stelletta) aurora, Hentschel, Aurora (hops) memhranacea (Hentschel) and Aurora 

 {Diastra) sterrastrcea Row. The sterrospherasters are identical with those of Row's 

 species, only somewhat larger*. In A. sterrastrcea, however, there are no trisenes, and 

 Row therefore very naturally included that species amongst the so-called Epipolasidse. 

 Aurora rowi undoubtedly represents very closely the actual stellettid species from which 

 Aurora [Diastra] sterrastrcBa was derived by loss of trisenes. The resemblance between 

 the two is remarkably close, even to the characteristic chocolate-brown colour. Unfortu- 

 nately Row's description of his species is faulty in certain respects. His account of the 

 cortex is very misleading. He has evidently included as part of the cortex a considerable 

 portion of the choanosome. The special layer of oxea which he describes in the supposed 

 deeper parts of the cortex, 0"5 mm. from the surface of the sponge, does not belong to the 

 cortex at all ; moreover it is not a properly defined layer but part of a confused general 

 skeleton. The mistake seems to have arisen through the lack of stained paraffin sections. 



Register No., Locality, &g. cxxxi., Seychelles, F. 9, 37 fathoms. 



Genus AsTEROPUS Sollas [1888]. 



Reduced Stellettidse which have completely lost their tetractinellid megascleres. The 

 main skeleton is a confused feltwork of large oxea. The microscleres are oxyasters and 

 sanidasters. 



I have already pointed out that Sollas regarded this genus as probably being derived 

 from either Stryphnus or Algol by loss of trisenes.. 



13. Asteropus simplex (Carter). 



(Plate 46, fig. 6.) 



Stellettinopsis simplex Carter [1879 b]. 



Asteropus simplex Sollas [1888]. « 



Asteropus haeckeli Dendy [1905]. 



Asteropus simplex Hentschel [1909]. 



Asteropus simplex Dendy [1915]. 



The single specimen in the collection is a cake-shaped mass about 90 mm. in maximum 

 diameter, flattened below and convex above. A few mammiform projections scattered 

 here and there on the upper surface are penetrated each by several narrow oscular tubes 

 and bear at their summits the rather small vents, most of which appear to be closed. 

 The surface is uneven and encrusted by a good deal of calcareous debris, together with a 

 species of Gelliodes. Texture firm, compact, coarse. Colour in spirit rather dark, purplish 

 brown. 



* Row gives the diameter of the full-grown sterrospheraster in Z). sterrastrcea as 0'36 mm. This is 

 obviously a mistake. I find it to be 0'028 mm. by actual measurement from the type. 



32—2 



