Geological Society. 461 



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 of 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 

 specimens the fibres were not disposed in the same manner as in the 

 sponge of commerce, but in a series of thin plates, resembling very 

 much the macerated woody fibres of the leaves of some endogenous 

 plants. Only one recent species, from Australia, is known to Mr. 

 Bowerbank to exhibit this structure. 



No spicula are mentioned by the author in either the agates or jas- 

 pers, and but one instance of the occurrence of foraminifera. The whole 

 of the sponges contained in the green jaspers, Mr. Bowerbank refers 

 to that division of the keratose which he has called Fistularia. 



2. Gemmules. — A specimen of Indian green jasper, which had under- 

 gone so great decomposition as to prevent the original fibrous structure 

 from being detected, presented innumerable globular vesicles of nearly 

 uniform size. Many of them were simple and transparent, and could 

 be recognised as organic only by the regularity of their size and form, 

 and by having universally dispersed over their outer surface minute 

 irregular black particles ; but by far the greater number of them 

 had in their interior a globular opake body, about one- third their 

 own diameter. Associated with these vesicles were numerous small 

 fibrous masses resembling minute keratose sponges, the largest of 

 which were five or six times the diameter of the vesicles ; but the 

 smallest were identical in nature with the nucleus, though in a higher 

 state of development. In other specimens from the same mass of 

 jasper, larger vesicles were found more sparingly imbedded amidst 

 the fibrous tissue of the sponge. From these characters and their 

 resemblance to those of the ova of some recent sponges, Mr. Bower- 



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



