OF THE SPONGIAD^E. 167 



1. Geodia, Lamarck. 4. Alcyoncettum, Quoy et 



2. Pachymatisma, Bower- Gaimard. 



bank. 5. Polt/mastia, Bowerbank. 



3. Ecionemia, Bowerbank. G. Halyphysema, Bowerb. 



7. Ciocali/pta, Bowerbank. 

 The second group contains : 



1. Tetltea, Lamarck. 3. Dictyocylindrus^QW&fo. 



2. ffalicnemia, Bowerb. 4. Phakettia, Bowerbank. 



In the whole of the first two groups, excepting Halypky- 

 sema, the skeleton radiations are fasciculated to a greater or 

 less amount in the different genera. 



The third group will comprise : 



1. Microciona, Bowerbank. 



2. Hymeraphia, Bowerbank. 



3. Hymedesmia, Bowerbank. 



The most striking general character in these three genera 

 is the extremely thin coating form of the sponge, and the 

 radiation of the skeleton spicula, either singly or in an ir- 

 regularly fasciculated form, from a common basal membrane, 

 the thickness of the sponge in some of the species being 

 less than the length of one of the radiating skeleton spicula. 



Suborder I. Spiculo-radiate skeletons. Not reticulate. 

 Composed of spicula radiating in fasciculi or sepa- 

 rately from the base or axis of the sponge. 



GEODIA, Lamarck. 



Skeleton. Spicula fasciculated, radiating from the base or 

 central axis of the sponge to the surface. Dennis 

 crustular, furnished abundantly with closely packed 

 ovaria. Ovaria siliceous, composed of cuneiform 

 spicula, firmly cemented together by silex, in lines 

 radiating from the centre of the ovary. Pores fur- 

 nished with cesophageal tubes, terminating in the 

 distal extremity of the intermarginal cavities. Inter- 



