on Moss Agates and other Siliceous Bodies. 543 



existence of vascular structure. The specimens were examined as 

 opake objects, with direct light concentrated by a convex lens. 

 The number of agates amounted to nearly 200, and that of green 

 jaspers to about 70. 



I . Fibrous structure. — Though polished agates afforded Mr, Bow- 

 erbank, in almost every specimen, strong evidence of spongeous origin, 

 yet the structure and arrangement of the fibres were seldom per- 

 fectly preserved throughout, presenting every intermediate state from 

 complete decomposition to the most distinct spongeous tissue. The 

 siliceous matrix of these remains exhibited a clear and frequently 

 crystalline aspect, but the prevailing tint of the enclosed organic 

 matter was bright red, brown, or ochreous yellow ; occasionally, how- 

 ever, the fibre was milk-white or bright green. The colouring mat- 

 ter, was generally confined within the bounds of the animal tissue, 

 leaving its surface smooth and uninterrupted ; sometimes it occurred 

 only in the interior of the tubular fibre, the sides being semipellucid 

 or milk-white ; whilst in other cases not only the fibre was com- 

 pletely charged with colouring matter, but the surface was also 

 slightly encrusted with it. In an agate believed to be from Sicily, 

 the greater part consisted of a confused mass composed of innume- 

 rable bright red fibres with no perceptible remains of surrounding 

 structure, but near the margin of the specimen the tubuli were as 

 perfectly preserved as in a recent sponge, presenting a semi-pel- 

 lucid and horny-looking substance enveloping red fibres. In those 

 instances in which the red pigment did not appear to have entered 

 the tube, the structure was best preserved, and Mr. Bowerbank 

 states that such ought to be the case, as the fibres of the Spongia 

 fistularis, though hollow throughout, are closed near the natural ter- 

 mination. The tubes in the Sicilian agate anastomosed in the same 

 manner as the fibres of the Mediterranean sponge of commerce, and 

 in the places where they were intersected they frequently exhibited 

 the internal cavity. These characters, the author remarks, prove 

 that the red fibre is the cast of the interior of the tube, and its dia- 

 meter, he adds, is as nearly as possible the same as that of the 

 hollow of the tube. In a moss agate from Oberstein the walls of 

 the best-preserved tubuli were charged with red pigment, and the 

 internal cavity was filled with pellucid silex, while the portion which 

 had suffered most from decomposition was a confused bright red mass 

 with obscure traces of fibrous structure. 



In the green jaspers from India the organic remains were found 

 to be generally better preserved than in the moss agates of Germany 

 and Sicily, and admitted pi being recognised as distinct species. 

 The green colouring matter was confined, with very few exceptions, 

 within the boundaries of the sponge-fibre, the surrounding matter 

 consisting of minute pellucid radiating crystals. Some of the spe- 

 cimens examined by Mr. Bowerbank were furnished with minute 

 contorted tubuli, very similar to those which are described in his for- 

 mer paper* as occurring upon the surface of chalk-flints. In other 



* Geol. Trans., 2nd Series, vol. vi. Part 1. 1841. 



