Chalk and Flint of the South-east of England. 87 
But if I have hitherto been unsuccessful in the microscopical 
exploration of our tertiary strata, an unexpected assemblage of the 
American miocene forms has been found in the digestive organs of 
certain living mollusca. Mr. Lee’s discovery of recent Coscino- 
disci in the barnacle (announced in the ‘ Medals of Creation’) has 
been followed up by his detection of numerous species and genera 
of infusoria in the stomach of the common scallop (Pecien mazt- 
mus*). These recent animalcules present almost all the genera and 
some of the species that prevail in the tertiary marls of Virginia ; 
in particular two very striking and abundant fossils of the Rich- 
mond earth, the elegant Coscinodiscus radiatus and the Dictyocha 
fibula. So close is the analogy, not only of the individual shields, 
but even of their collocation, that it would be difficult for an ex- 
perienced observer to distinguish slides mounted with the re- 
spective organisms, although the one group is from deposits of 
unfathomable antiquity, and the other from the British seas. 
I have already stated that the modern calcareous deposits of 
the Bermuda Islands contain layers of infusorial earth ; these are 
made up of organisms resembling those of America and the recent 
species found in the scallop. 
One more fact in connexion with this subject remains to be 
mentioned. Along the shore of the Sussex coast to the east of 
Brighton, a bed of sand and calcareous mud, the detritus of 
the neighbouring cliffs, is in the progress of formation ; and in 
this sedimentary deposit my son, Reginald Neville Mantell, has 
discovered shells of recent Rotalie, Nodosarie, and other poly- 
thalamia, associated with the siliceous shields of Coscinodisci, Dic- 
tyoche, and other infusoria, and with fossil Rotalie and Texti- 
larie from the chalk. Were then at the present moment a deposit 
is in progress, whose organic contents consist of an assemblage 
of the living species of the animalcules of the present sea with the 
fossil forms of the ancient chalk ocean ; in like manner in the bed 
of the Nile, the polythalamia of the Nummulite rock are being 
imbedded with the existing mollusca of that river: collocations 
of this nature may perhaps exercise the ingenuity of the geolo- 
gists of future times, and give rise to speculations of as little 
value as some of those with which I have ventured to trespass on 
the indulgence of the Society. 
In conclusion I would remark, that the preceding observations 
are the result of the examination of organisms within the reach 
of the best microscopes which modern art has produced ; yet 
there can be no doubt, that if the powers of ow instruments 
could be increased, fossil structures yet more minute and far 
* See Annals of Nat. Hist. April 1845. 
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