272 REVISION OF THE MOXAXONID SPONGES, i., 



iii. Another specimen, also labelled from Port Jackson, agrees 

 with those of the two preceding forms in having chiefly stylote 

 megascleres and asters of two kinds; but the spherasters are 

 extremely abundant throughout the entire cortex and occur 

 fairly plentifully also in the choanosome, decreasing in number, 

 however, towards the centre of the sponge. Many of the mega- 

 scleres are blunt-pointed, and an appreciable number of them 

 approximate in form to (fusiform) strongyla; their maximum 

 size is about 1520 by 22 /x. The sphei*asters, the largest of which 

 measure 7 b ji in total diameter, have from 13 toll (actually 

 countable) rays; the rays vary from one-half to three-fourths the 

 diameter of the centrum in length, and are often slightly curved, 

 and occasionally forked, at the extremity. In the choanosome, 

 spherasters of all sizes, from 20 /x in diameter upwards, are com- 

 mon. As regards the tylasters, the same remarks apply as to 

 those of the preceding forms. Radially directed megascleres, 

 lying between the fibres, are not so abundant in this as in the 

 preceding forms, and the surface of the sponge is hispidated by 

 far-projecting spicules. 



iv. The specimens labelled ^''Tethya fissurata, Port Molle," differ 

 from the foregoing, and agree with one another, in the following 

 particulars : (1) the megascleres of the fibres^ the maximum size 

 of which somewhat exceeds 2000 by 40 /*, are invariably rounded 

 at the apex and are usually almost or quite symmetrically-ended 

 (fusiform strongyla); (2) the megascleres between the fibres are 

 distinctly different from the fibre-spicules (being more or less 

 sharp-pointed at the apex and of much smaller size than them); 

 (3) the chiasters are of two kinds, tylasters and "oxyasters"; 

 and (4) the spherasters have from 19 to 23 actually countable 

 rays. As in the third-mentioned variety, the spherasters are 

 closely packed throughout the entire cortex and occur also 

 scattered in the choanosome. The tylasters, measuring at most 

 16/x in diameter, have the ends of the rays slightly expanded 

 and provided with minute spines. The asters of the third kind 

 attain to 23 /x in diameter, and have comparatively slender rays 

 which are not expanded at the extremities, and which usually are 

 blunt-pointed and provided along their whole length with not 



