100 



to the same species with the last described : a difference is, however, 

 observable in the appearance of the two fossils. This fossil, which 

 is silicious, has been divided transversely by the lapidary. Fig. 11 re- 

 presents the external surface of its superior part, and Fig. 13 the po- 

 lished interior surface of the inferior part. In Fig. 11 it will be seen, 

 that a slight cavity appears in that part in which, in the former fossil, 

 Fig. 12, a moderate degree of prominency had been formed; and that 

 in this fossil ramifying depressions are perceived in that part, on which, 

 in the former specimen, raised ramified filaments are to be seen. On 

 the polished surface of the interior part, numerous minute cavities are 

 observable, and which, particularly near to the centre, resemble the lit- 

 tle chambers for the lodgment of the pips or seeds of the pomaceous 

 fruits. 



These appearances and apparent differences seem, however^ to be 

 sufficiently easy of explanation, without having recourse to the sup- 

 posing of any difference between the two original bodies, from which 

 the two fossils have proceeded. It appears to be exceedingly probable 

 that, in the former fossil, the silicious impregnation, which appears to 

 have been to saturation, had pervaded not only the whole of thespon- 

 geous part, but even the harder filamentous part ; whilst in the latter 

 fossil, the silicious impregnation which seems to have been much less 

 abundant, has only impregnated the spongeous part and the filamen- 

 tary part, not having been thus impregnated, has not been preserved. 



The fossil, Plate IX. Fig. 1, which is a dark flint found in one of our 

 English chalk-pits, and which derives from the chalk the colour on its 

 surface, is a highly interesting and instructive specimen of this species. 

 The numerous ramifying filaments proceeding from the circular body 

 at its superior part, all terminate in, or rather appear to pass beneath 

 the line which is formed by a seemingly added substance, which covers 

 the whole of the inferior parts. The feeling yielded by the handling 

 of this specimen, excited a suspicion as to the nature of the substance 

 with which it is partially invested. On being handled, it occasions a 



