14 Mr. J. S. Bowerbank on Moss Agates 



spongeous tissue ; and generally speaking, the organic struc- 

 ture is in a better state of preservation than it is in the moss 

 agates of Germany and Sicily. The green colouring matter 

 in these siliceous mosses is found, with very few exceptions, 

 to be confined within the boundaries of the sponge fibre, the 

 surrounding siliceous matter consisting of minute pellucid ra- 

 diating crystals, which have for their bases the sponge fibres, 

 amid which they have been deposited. Upon taking some 

 small thin pieces from various parts of a large mass of this 

 mineral in the possession of Mr. Tennant, I found every frag- 

 ment of it to abound with beautifully preserved ramifying 

 sponge fibres ; and upon examining numerous small rough 

 specimens of this substance, some of which I obtained from 

 the same gentleman, and others from a lapidary inClerkenwell, 

 I found the whole of them to abound, in a similar manner, 

 with well-preserved fibres of various species of sponges. On 

 a few of these small rough specimens a portion of the natural 

 external surface remained ; and upon examining this as an 

 opake object with direct light and a microscopic power of 500 

 linear, I found some of them to be furnished with minute 

 contorted tubuli very similar to those which I described in a 

 former paper as occurring upon the surface of chalk flints *. 

 Upon examining some very dark-coloured polished specimens 

 of a green jasper which I obtained from Mr. Tennant, I found 

 the spongeous structure in a more perfect state of preserva- 

 tion than in any of the specimens previously examined. 



The fibres in this case are not disposed in the same manner 

 as in the sponges of commerce, but are arranged in a series 

 of thin plates, resembling very much in their appearance por- 

 tions of macerated woody fibres of the leaves of some endo- 

 genous plants. This singular form of tissue I believe to be 

 exceedingly rare among recent sponges, as I have met with it 

 in but one species which came among the large collection of 

 sponges received from my friend Rupert Kirk, Esq., of Syd- 

 ney, who obtained them on the coast in that neighbourhood. 

 On examining about seventy thin sections of green jasper 

 which I obtained from a lapidary in Clerkenwell, and which 

 were said to have been imported from India, I found the re- 

 sults equally satisfactory : every specimen afforded undeniable 

 evidence of spongeous origin, and in the greater part of them 

 the organic structure was in so perfect a state of preservation 

 as readily to admit of their being recognised as distinct spe- 

 cies. Among this series of specimens there were several slices 

 which had evidently been cut from the same mass which pre- 



* Transactions of Geological Society of London, New Series, vol. vi. 

 p. 183, pi. xviii. fig. 2. 



