10 Mr. J. S. Bowerbank on Moss Agates 



the interstices of the horny fibre are filled with a semipellucid 

 fleshy matter, in which numerous spicula are found imbedded. 

 I will not enter into a lengthened detail of the investigations 

 of these recent forms, as they have already been given to the 

 public in two papers. The first " On the keratose sponges 

 of commerce," I had the honour to read before the Micro- 

 scopical Society of London on the 27th of January 1841*, and 

 the second " On the structure of a keratose sponge from Au- 

 stralia," is published in the ' Annals and Magazine of Natural 

 History,' April 1841. It is necessary to state thus much, as 

 the discovery of siliceous spicula in recent sponges removes 

 the discrepancy that appeared to exist between the recent and 

 the modern types of a portion of the animals under consider- 

 ation. The fibre in all the sponges of commerce, as well as in 

 many keratose species from Sydney, that I have examined, 

 is solid; but in one species, Spongia fistularis, Lamarck, de- 

 scribed by Dr. Grant in the e Edinburgh Philosophical Journal/ 

 vol. xiv. p. 339. the structure is truly tubular ; and this is the 

 only recent type of the form that I am acquainted with, al- 

 though, as it will be hereafter seen, this tubular form of the 

 fibre is of frequent occurrence in the fossil sponges. 



The results arising from the examination of the siliceous 

 bodies of the chalk, greensand and oolitic formations, induced 

 me to extend my researches to other siliceous masses ; and with 

 this view I obtained, through the kindness of Mr. Tennant, a 

 considerable number of polished specimens of moss agates 

 from Oberstein in Germany, from Sicily, and other localities. 



I examined these specimens as opake objects by direct 

 light concentrated on their surfaces by the application of a 

 convex lens, and in many cases the results of the examination 

 far exceeded my expectations of being able to detect the or- 

 ganic structures imbedded in them. Upon a minute and 

 careful examination of numerous polished slabs of the moss 

 agates of Oberstein, almost every specimen presented strong 

 evidence of their spongeous origin. The structure and ar- 

 rangement of the fibre of the sponge is rarely to be found in 

 a state of perfect preservation throughout the whole of the 

 mass, but usually presents the appearance of having suffered 

 to a great extent by maceration and disruption of its compo- 

 nent parts previous to its fossilization. Generally speaking, 

 the fibres adhere together in confused and ropy masses, with 

 here and there one or two in a somewhat better state of pre- 

 servation, and occasionally, especially near the external sur- 



* Published in the Transactions of the Microscopical Society, part the 

 first, vol. 1, p. 32. 



