THE FAMILY OF THE DESMACIDINAE. Ill 



as the yet living' stock of Esperia, Desmacidon and Myxilla^ 

 in which the distinctive character of either of those , has 

 not yet made its appearance. We have here , so to say , 

 the materials , that may yet prove to be useful in the struggle 

 for hfe. So for instance : the skeleton can be strengthened 

 by keratode-fibre , and in this way a Desmacidon would 

 appear ; the varying achors of Amphilectus become equiended 

 in Desmacidon and Myx'dla , inequiended in Esperia. Even 

 though we cannot at first understand , why it should be 

 more useful for a Sponge to have inequiended anchors 

 than equiended ones , or the contrary , still we may sup- 

 pose that in some way or other there is a certain benefit 

 attached to it. 



And so I have united in this new genus those species which 

 stand between Esperia and Desmacidon by the simultaneous or 

 varying appearance of symmetric or asymmetric anchors. 

 Further those species , which do not distinctly show the 

 characteristics of Desmacidon and Myxilla ; finally — although 

 as yet only provisionally — all those species which are 

 so imperfectly described , that the question cannot be de- 

 cided. In this case it may be supposed that certain cha- 

 racteristics of the above mentioned genera did not very 

 distinctly show themselves. 



Speaking in a Haeckeiian sense, one may regard Ayn- 

 philectus as the principal genus ; Esperia , Desmacidon and 

 Myxilla as generic varieties. 

 1. Atnphilectus gvucilis (Bwk.) Vosm. 



Synon. Isodictya gracilis Bwk. 'QQ. 

 Isodictya Edwardii Bwk. 'QQ, 

 Isodictya paupera Bwk. '66. 



Litt. Bowerb. M. Br. Sp. II p. 331 , III p. 149.— 

 Bowerb. M. Br. Sp. II p. 325, III p. 148.— 

 Bowerb. M. Br. Sp. II p. 328, III p. 139. 



Spic. tr. ac. (two kinds.) 



anc".2 („minute, few in number.") 



Loc. Lough Larne (Ireland). — Banfli'. (Scotland). — 

 Torquay. 



Note* tvoxa. the Leyden Museui», Vol. II. 



