AND PHYSIOLOGY OP THE SPONOIAD^ 
1119 
Spongia officinalis, we shall then have the type of the first suborder of the order 
Keratosa, distinguished by the above characters. There are two genera belonging to 
this suborder; the first of these is Spongia, Linnaeus. Its character is as follows: — 
Spongia, Linneus. 
Skeleton kerato-fibrous. Fibres solid, cylindrical, aspiculous. Eete imsynimetrical. 
Type, Spongia officinalis, Linnaeus. 
The number of species of Spongia appear to be very considerable ; and in all of them 
the irregular meandering character of the skeleton-fibre readily serves to distinguish 
them. Plate LXXIV. fig. 9, and Part II. Plate XXVII. fig. 7. 
The second genus is founded on the specimen described by Soweeby in the ‘ British 
Miscellany,’ p. 87, plate 48, and named by him Spongia pulchella. I fortunately have 
this specimen ; and on carefully examining it I find it to possess all the characters of the 
genus Spongia, excepting that the reticulations of the skeleton are very symmetrical ; 
and this is so important a structural difference that I have thought it advisable to 
constitute it the type of a new genus, the characters of which are as follows : — 
Spongionella, Bowerbank. 
Spongia, Sowerby and Johnston. 
Skeleton kerato-fibrous. Fibres solid, cylindrical, aspiculous. Eete symmetrical ; primary 
fibres radiating from the base to the apex. Secondary fibres disposed at nearly 
right angles to the primary ones. Plate LXXIV. fig. 10. 
Type, Spongia pulchella, Sowerby. 
Suborder II. Solid, semispiculate, kerato-fibrous skeletons. 
The sponges of this suborder closely resemble in general appearance those of the 
genus Spongia, but they differ very considerably in the structural characters of their 
skeletons, which consist of a somewhat irregular radiation of primary fibres from the 
base towards the apex of the sponge, Avith an unsymmetrical series of secondary fibres 
emanating from and connecting together the series of primary ones. 
The primary fibres are compressed and broad in their form, frequently three or four 
times the width of the diameter of the surrounding cylindrical secondary ones. But 
their most striking character is their possessing a considerable number of siliceous 
spicula, which are irregularly imbedded in their centres ; sometimes the series of spicula 
within the fibre consists of but one or two beside each other, and at other times they 
are numerous and very irregularly disposed. This central series of spicula appears to 
exist only in the primary fibres ; and I have never been able to detect the slightest indi- 
ilDCCCLXII. 7 N 
