782 NEW GENERA OF MONAXONID SPONGES, 



slightly beyond, the dermal membrane. These radial columns 

 are usually not much longer than the largest spicules composing 

 them, — thus approximating in character rather to bundles or 

 tufts; are unconnected by transverse fibres or spicules; and 

 are entirely unprovided with spongin except proximally for a 

 short distance beyond their origin from the longitudinal fibres. 

 Outside the axial skeleton, in a narrow zone immediately sur- 

 rounding it, there also occur numerous long slender auxiliary 

 styli directed longitudinally. The dermal skeleton is composed 

 of numerous parallel or slightly penicillate tufts of the same 

 spicules, the extremities of which usually project somewhat be- 

 yond the surface. 



The microscleres are numerous isochelae palmatae and scarce 

 toxa, the former occurring most abundantly in the superficial 

 layers of the sponge and only very sparsely within the inter- 

 stices of the axial skeleton, whilst the toxa are almost entirely 

 confined to the latter region of the skeleton. 



Megascleres. — (i.) The styli (Text-fig. 2, a) which core the 

 fibres of the axial skeleton are slightly curved, and of nearly 

 uniform diameter throughout the greater part of their length, 

 tapering, thence gradually to a sharp point. They range in 

 size from about 260 by 7/x or less to occasionally slightly up- 

 wards of 375 by 15^. The largest of them approximate closely 

 both in form and size to the smallest of the "radial" styli. 



(ii.) The styli (Text-fig. 2, b) composing the radial columns 

 range in size from rarely less than 400 by 16^. up to 690 by 

 24/x. They also are slightly curved and gradually sharp-point- 

 ed, but they differ from the preceding styli in being usually 

 more or less narrowed towards the base. 



(iii.) The auxiliary or dermal styli (Text-fig. 2, c) are mostly 

 straight or nearly so, somewhat gradually sharp-pointed, and 

 also slightly attenuated towards the base. They range in length 

 from about 250 to 710/x,, and in diameter up to 9.5/u,. 



Microscleres. — (i.) The isochelae palmatae (Text-fig. 2, d) 

 are of the usual Clathria type, and measure from 9 to 24/a in 

 length. They are very nearly divisible into two groups with re- 

 spect to size — individuals between 15 and 18/x in length being 

 extremely rare. 



(ii.) The toxa, which are rather scarce, are of the form shown 

 in the figure (Text-fig. 2, e). They are characterised by the 

 great degree of their bending, and by the not uncommon occur- 



