OP THE SPONGIADyE. 205 



the Linnean Society of London,' vol. xxii, p. 117, plate 

 xxi. 



The fibres in Farrea occa are rather coarse, abundantly 

 tubercnlated, and the mode of reticulation is rectangular. 

 Their construction is exactly like those of Verongia, the 

 type of the fourth suborder of the third order, Keratosa. 

 Pig. 277, Plate XV, represents one of the simple fistulose 

 spiculated fibres from the skeleton of Farrea occa, Bower- 

 bank, MS., X 108 linear. 



Order III. KERATOSA. 



Suborder I. Solid non-spiculate kerato-fibrous skeletons. 



The greater number of the sponges of commerce belong 

 to this suborder. How many species are comprised under 

 the designation of " the sponges of commerce " it is very 

 difficult to decide, as we rarely obtain them in their 

 natural condition, but it is certain, from their well- washed 

 skeletons, that their number is considerable, and that at 

 least two distinct genera occur among them. If we 

 assume that the well-known cup-shaped sponge, usually 

 sold as the best Turkey sponge, is the one entitled to the 

 designation of Spoiigia officinalis, we shall then have the 

 type of the first suborder of the third order Keratosa dis- 

 tinguished by the above characters. There are two genera 

 belonging to this suborder ; the first of these is Spongia, 

 Linna3iis. Its character is as follows : 



SPONGIA, Linnaus. 



Skeleton kerato-fibrous. Fibre solid, cylindrical, aspiculous. 

 Rete unsymmetrical. 



Type, Spongia officinalis, Linnaeus. 



The number of species of Bpongia appear to be very 

 considerable, and in all of them the irregular meandering 



