(ifiO REVISION OF THE AXINELLID.E, iii., 



Spongin is present in relatively small quantity. The megascleres 

 are imperfectly differentiated into three kinds: (i.) curved oxea 

 forming the skeleton-reticulation, attaining a maximum size of 

 from 560x14 to 700 x 18/x; (ii.) longer and slenderer, scarce 

 styli, strongyla, and (very rare) oxea, occurring interstitially, 

 ranging in length to upwards of 900/a; and (iii.) smaller inter- 

 stitial and dermal oxea, connuonly between 250 and 350/a in 

 length and 4 or 5/i. in diameter, but frequently slenderer, and 

 connected by spicules of intermediate size apparently both with 

 (i.) and (ii.). The acanthoxea are from 40 to 130/ji in length and 

 up to 4 or 5ji. in diameter exclusive of the spines, and rather 

 seldom exhibit a bulbous dilatation. 



ioc— Port Phillip. 



External characters. — The general shape and habit of growth 

 of the sponge are sufficiently indicated in the diagnosis; and the 

 characteristic rugose surface-af)pearance produced by crenated 

 longitudinal ridges and intervening furrows is well shown by the 

 figure (PI. xxix., fig. 6), — which also illustrates the most frequent 

 form of the sponge, viz., one intermediate between flabellate and 

 submassive. Apparently it is only in its younger stages that 

 the sponge is massive, subsequent growth taking place chiefly in 

 height and bi'eadth, with only slight increase in thickness; 

 occasionally the plate thus formed, instead of remaining simply 

 flabellate, becomes somewhat irregular through formation of 

 perpendicular lateral outgrowths similar to itself. The largest 

 specimen at my disposal measures about 75mm. in height, 1 10mm. 

 in breadth, and 25 mm. in maximum thickness of the plate. The 

 surface-ridges (and furrows) pass without discontinuity across the 

 margin of the S23onge fi'om one side of it to the other, and, as 

 necessarily follows, are oppositely situated on the two surfaces. 

 The oscula are situated marginally, and are numerous and of 

 small size, the largest seldom exceeding 1 nun. in diameter. The 

 dermal membrane, which is well-developed, is most distinct 

 within the surface-grooves, whei'e it is underlain by extensive 

 subdermal s^oaces; it is closely perforated with minute pores, 

 which in some places are sufficiently lai'ge to be discerned with 



