Catalogue of Non-Calcareous Sponges. 29 



Skeleton. The main skeleton is a dense, irregularly isodictyal 

 network of oxea. Towards the surface this is rej)laced by 

 radiating, branching whisps of tylota. 



Megascleres, (a) rather slender, slightly curved, smooth oxea, 

 gradually sharp-pointed at each end, measuring about 0'2 by 

 0"008 mm. (very rarely a stylote spicule occurs amongst them) ; 

 (l>) tylota, with well-developed oval heads, smooth, straight ; 

 about 0-25 by 0-005 mm. 



Jfieroscleres, (a) tridentate isochelai like those of Alyxilla ; 

 fairly stout and about 0-028 mm. long, but varying in size ; 

 (^) Sigmata, small, slender, simple and contort, about 0-02 mm. 

 from bend to bend. 



R.N. 361 (s. 15, 3 f; "bright orange red") ; 451 (s. 9, 17 f; 

 "rufous"); 662 ; 673 (s. 10) ; 717 (s. 10) ; 7' 8 (Sorrento Reef); 

 719 (Sorrento Reef); 722 (Sorrento Reef); 836 (s. 10); 837 

 (s. 10); 838 (s. 10); 845 (s. 10); 861 (s. 9); 903 (s. 10); 

 919 (s. 10); 997 (s. 14). 



Sub-family Ectyonin.e. 



Skeleton fibre echinated by laterally projecting styli, usually 

 spined. 



Genus Afyxilla, Schmidt. 



Main skeleton reticulate, composed of usually spined styli, and 

 sometimes echinated by spined styli or tylostyli of different form. 

 Variously ended diactinal megascleres are also present, chiefly at 

 the surface. There is usually very little spongin. Microscleres 

 tridendate isochelae, to which sigmata may be added. 



Seeing that the type of this genus, Af. rosacea, has no special 

 echinating spicules, I cannot agree with Topsent in separating 

 such forms as a distinct genus under Gray's name Dendoryx. 

 Myxilla has several years' precedence over Dendoryx, and at 

 present I propose to retain the name Myxilla both for species 

 with and species without special echinating spicules {vide 

 Challenger Report). Similarly, Topsent's Lissodendoryx falls 

 under Myxilla, for the degree of spination of the styli varies so 

 much that it is impossible to draw a hard and fast line between 

 the two. 



