R. W. H. ROW—REPORT ON THE SPONGES : NON-CALCAREA. 303 
the centrum being only represented by the fused ends of the rays. The 
largest specimen in which the actines retained their original sharply pointed 
condition was 0:17 mm. in diameter. The further growth takes place by 
elongation and thickening of the rays, but they do not seem to increase 
very much in number. In the fully-grown spicule the rays have developed 
slightly expanded heads, very similar to those of a true sterraster. The 
spicule never becomes absolutely solid, however, and the ends of the rays can 
always be distinguished, projecting from 3 to 5 w from the central mass. 
The fully-grown spicule measures 0°36 mm. in diameter. There is no 
hilum such as is found in a typical sterraster. 
In an account of the sponges of South-Western Australia, Hentschel (15) 
hes described a species of Stelletta (S. aurora) which possesses somewhat 
similar spherasters to those of the species under consideration, especially in 
the variety arenosa: the rays are again numerous and are swollen and 
finger-like, but instead of the enlarged terminations which occur in Diastra 
sterrastrea the ends are provided with minute spines. Also the coalescence 
of the rays has not gone quite so far in S. awrora as in Diastra sterrastrea, 
but otherwise the spicules are very similar. 
It is also noteworthy that in Stelletta aurora var. arenosa the heads of 
some of the triznes are evidently becoming obsolescent, so that there is 
considerable evidence furnished by these two species—<Stelletta aurora and 
Diastra sterrastrea—of a direct descent of the family Epipolasidee from the 
Stellettidee. 
Gi.) A small spheraster occurs scattered throughout the sponge, both 
cortex and choanosome, and forming a very dense dermal layer immediately 
beneath the surface. They consist of a comparatively large centrum, from 
which arise short knob-like rays. The size of the spherasters varies con- 
siderably, the largest being about 0°009 mm. in diameter. 
Locality. The single specimen was obtained at Khor Dongonab. 
Distribution. Red Sea. 
Family Tetsayiv 4. 
Astrotetraxonida with stylote megascleres and euasters for microscleres, 
with strongly developed fibrous cortex and radialiy arranged skeleton. 
TmTHYA SEYCHELLENSIS. 
Synonymy :— 
1881. Alemo seychellensis, Wright (36). 
1884. Tethya cliftont (Bow.), Ridley (23). 
1888. Tethya seychellensis, Sollas (29). 
1891. Tethya seychellensis, Keller (18). 
There are three specimens in the collection. Two are rather small 
specimens, about 30 mm. in diameter. They each possess a single osculum, 
LINN. JOURN.—ZOOLOGY, VOL. XXXE, oy 
