Classification of the Spongida. 



Order VII. HEXACTINELLIDA. 



Fie:. 6. 



131 



Spicules characteristic of the Hexactinellida : a, sexradiate type ; 

 b, acerate type ; c, sexradiate cross in the centre. 



Possessing a skeleton charged with proper spicules. Spicules 

 all based on a sexradiate type, as indicated by their forms and 

 the presence of a sexradiate cross at the centre of the spicular 

 canal. 



Order VIII. CALCAREA. 



Fig. 7. 



Characteristic spicule of the Calcarea. 

 Possessing calcareous spicules only. 



Families*. 

 CARNOSA. 

 Family 1. Halisarcida. 

 Possessing no spicules. 



Family 2. Gumminida. 



Possessing spicules. 



* In endeavouring to carry out what I proposed in my " Prefatory 

 Remarks" respecting the classification of the Spongida into "Orders, 

 Suborders, and Families," I find, on arriving at this point, that our know- 

 ledge of these beings is not sufficient for doing it further than the eight 



9* 



