274 REVISION OF THE MONAXONID SPONGES, i., 



sponges, with a Hat base," they are stipitate, with a spherical 

 body (in each specimen about 40 ram. in diameter), and with a 

 well-developed, fairly stout stalk which divides below into a 

 number of root-like processes (Plate xv., fig.3). They correspond 

 exactly with the description with respect to surface-features, as 

 may be seen from the figure which I furnish of one of them; and 

 they also show considerable agreement in other respects. The 

 description, however, makes it appear as if only one form of 

 aster, a small tylaster, was present in addition to spherasters, 

 whereas an oxyaster is also present; but Lendenfeld mentions 

 that " a great abundance of the young stages of the larger kind 

 of stellate is to be found," and I, therefore, take it that he mis- 

 took the oxyasters for developmental forms of the spherasters. 

 A more correct account of the spiculation is as follows : — 



The spicules of the radial fibres are almost exclusively fusiform 

 strongyla with one extremity (viz., the outwardly directed) some- 

 what nai-rower than the other, and attaining a maximum size of 

 about 4000 by (rarely) 80 /x; the terminal spicules of the fibres, 

 however, which project beyond the surface, are usually more or 

 less sharp-pointed and are not so large as the others. Between 

 the fibres, megascleres (styli and strongyla) of smaller size occur, 

 but are rare. 



The spherasters are incompletely differentiated into two kinds: 

 (l)a relatively shorter-rayed, ranging in total diameter from 

 about 45// to upwards of 160//., and having from 13 to 18 actually 

 countable rays of length seldom exceeding (and when least, only 

 about two-thirds) the diameter of the centrum — the number and 

 relative length of the rays decreasing as the size of the spicule 

 increases; and (2) a relatively longer-rayed, ranging in diameter 

 from less than 75 /x up to 240 /x, and having from 10 to 14 count- 

 able rays, the length of which is greater than (and occasionally 

 attains to twice) the diameter of the centrum. The former occur 

 only in the cortex, and in some parts of it are abundant through- 

 out its entire thickness; the latter are chiefly confined to the 

 choanosome, where they are extremely abundant in the peripheral 

 layer and gradually diminish in number towards the centre. 

 Frequently in the case of the longer-rayed spherasters, and ex- 



