INTRODUCTION. IX 



R. dura or densa Nardo. A Desmacidon, in the 

 structure of its skeleton rete, but of a closer and more 

 compact arrangement than in any of our British 

 species. 



I received specimens of two species of Cacospongia 

 Schmidt, G. Mollior, and G. Sralaris. The former 

 proved to be a true spongia, with the slender, solid 

 fibrous texture of the Turkey sponge of commerce, 

 while the latter was an undoubted Yerongia with the 

 strikingly characteristic large inflexible canaliculated 

 fibres so distinctly illustrative of that genus. The 

 slightest microscopical examination of their structural 

 peculiarities would have served at once to distinguish 

 them as anatomically distinct genera. 



In six species of Reniera therefore, we have three 

 distinct types of organisation. Halichondria with the 

 irregular and indefinite spiculo-reticulate structure of 

 its first division. Isodictya with its regular scalari- 

 form spicular reticulation, and the widely separated 

 skeleton of Desmacidon, composed of spiculo-fibrous 

 structure. If this amount of structural discrepancy 

 occurs in the examination of six specimens said to 

 belong to the same genus, we may readily imagine the 

 amount of confusion of structural character that we 

 might expect to find in a more extended examination 

 of the species referred to the genus Reniera by 

 Professor Schmidt. 



The three species of Esperia of which I received 

 small portions all proved to belong to my genus 

 Raphiodesma. 



E. timicata, Schmidt. Has acuate spicula and is 

 closely allied to the British species R. lingua, but 

 differs from it in having a profusion of small stout 

 acerate tension and defensive spicula immediately 

 beneath the dermis. 



E. Bowerbankii, Schmidt. Has also acuate spicula. 



E. Indian Ocean. Is not named. It is a very 

 strongly characterised species. 



