THE FAMILY OF THE DESMACIDINAE. 99 



NOTE XVIII. 



THE SPONGES OF THE LEYDEN MUSEUM. 

 I. The family of the Desmacidinae. 



BY 



G. C. J. VOSMAER. 



The Leydeii Museum of Natural History possesses a col- 

 lection of Sponges, which have never as yet been tho- 

 roughly examined nor classified in accordance with the 

 progress , which has lately been made in this branch of 

 science. 



And so it was with much pleasure that I accepted the 

 honourable task of determining and arranging this collection , 

 being at the same time convinced of the necessity of trea- 

 ting the different groups separately. 



In the following paper I propose to treat of the family 

 of the Desmacidinae, siliceous Sponges which by their an- 

 chors , bows and bihamate (S- shaped) spicules form a very 

 distinct group. 



Generally speaking the determination of Sponges affords 

 peculiar difficulties. Almost every species varies conside- 

 rably : it is very rare that a Sponge forms a so called 

 „good species." Even with the aid of Haeckels' splendid 

 monograph one very often remains in doubt about the 

 name of certain species of calcareous Sponges. This is 

 still more the case with siliceous Sponges, the literature 

 of which is so widely spread in different periodicals. 



Note» from the Leyden Miuseuxxi, "Vol. II. 



