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 
represents the external surface of its superior part, and Fig. 13 the 
polished 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 
little 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 supposing 
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 the spongeous 
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 filamentary part, not 
having been thus impregnated, has not been preserved. 
The fossil Plate IX. Fig. 1, M'hich 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 
