1862.] 



147 



The first of these orders (Calcarida) has hitherto been repre- 

 sented by the genus Grantia only ; but as the genus as established 

 by Fleming contains sponges having very differently constructed 

 skeletons, the author has divided the whole of the species of calcareous 

 sponges that have been named and described into the four following 

 genera, Grantia, Leucolenia, Leuconia, and Leucogypsia, in accord- 

 ance with four distinct types of skeleton-structure which are found to 

 exist among the sponges originally arranged under the genus Grantia 

 of Fleming. 



The second order, Silicea, is very much more extensive than that 

 of Calcarea, and, from the striking varieties it affords in the con- 

 struction of the skeletons, it allows of a subdivision into seven sub- 

 orders. The first of these consists of sponges having spiculo-radiate 

 skeletons, and contains thirteen genera, as follows : Geodia, Puchy- 

 matisma, Ecionemia, Alcyoncellum, Polymastia, Halyphysema, 

 Tethea, Halicnemia, Dictyocylindrus> Phakellia, Microciona, By- 

 meraphia, and Hymedesmia. 



The second suborder consists of spiculo-membranous sponges ; it 

 consists of one genus, Hymeniacidon. The third has spiculo-reticulate 

 skeletons ; it contains four genera, Halichondria, Hyalonema, Iso- 

 dictya, and Spongilla. The fourth suborder has spiculo-fibrous 

 skeletons ; it contains two genera, Desmacidon and Raphyrus. The 

 fifth suborder has compound reticulate skeletons ; it has but one 

 genus, Diplodemia. The sixth suborder has solid siliceo-fibrous 

 skeletons ; it contains one genus, Dactylocalyx. The seventh sub- 

 order has canaliculated siliceo-fibrous skeletons, and contains one 

 genus, Farrea. 



The third order, Keratosa, is also divided into seven suborders. 

 The first, consisting of solid non-spiculate kerato-fibrous skeletons, 

 is represented by one genus, Spongia ; the legitimate type of the 

 genus being the cup-shaped and finest Turkey sponges of commerce. 

 The second suborder has solid semi-spiculate kerato-fibrous skele- 

 tons ; it contains at present but one genus, Halispongia ; the type 

 of which is the coarse massive sponges of commerce from the West 

 Indian Islands. The third suborder has solid, entirely spiculated 

 kerato-fibrous skeletons ; it has one genus, Chalina : the type of 

 this genus is one of the commonest of the British sponges, Halichon- 

 dria oculata of Johnston. The fourth suborder is characterized by 



