Mr. H. J. Carter on known Fossil 8])onges. 281 



(p. 822). And, tliirdlj, that the qnantitj of the horny- 

 tibred sponges, particularly from the sea on the south coast of 

 Australia and that about the West-India Islands, in the col- 

 lection at the British Museum, far surpasses all the rest in 

 bulk and number of species. 



Here I must, for the sake of convenient reference, insert 

 a note of my Classification of 1875 (' Annals,' vol. xvi. p. 128 

 &c.) : — 



Class SPONGIDA, Huxley. 

 Order I. Carnosa. 



Without evident skeleton. 



Order II. Ceratina. 



Possessing a skeleton composed of horny (now called 

 " spongin ") fibre, with a granular, chiefly hollow, core, con- 

 taining for the most part no foreign bodies. 



Order III. Psammonemata. 



Possessing a skeleton composed of solid fibre more or less 

 cored with foreign bodies (grains of sand, fragments of sponge- 

 spicules, &c.). 



Order IV. Rhaphidonemata. 



Possessing a skeleton composed of horny fibre with a core 

 of " proper spicules " (that is, spicules produced by tiie 

 sponge itself). Spicules chiefly simple acerate, and chiefly 

 confined to the interior of the fibre. 



Order V. Echinonemata. 



Possessing a skeleton composed of horny fibre cored with 

 " proper spicules " internally and echinated with " proper 

 spicules " externally. Form of spicule chiefly acuate. 



Order VI. Holorhaphidota. 



Possessing a skeleton whose fibre is almost entirely com- 

 posed of " proper spicules " bound together with a minimum 

 of sarcode (spongin). Form of spicule variable. 



Order VII. Hexactinellida. 

 Possessing a skeleton charged with " proper spicules," all 



