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an equal degree, nor indeed a similar kind, of brilliancy with that of 
the former shell. I have several specimens of fossil mother-of-pearl 
from the Nautilus ; but, where the colours are not entirely lost, the 
appearance is exactly similar to that of the recent substance. 
Specimens of the Cornu ammonis, on which the brilliant nacre still 
exists, are sometimes found. At Broad Marston, as we are informed 
by Dr. Maton *, a stratum was found, in 1778, containing a congeries 
of Cornu ammonis, on which the nacre is still visible : and indeed, 
on some of these, the brilliancy of colour possessed by the nacre is 
very considerable. The finest British specimens of this kind, which I 
have seen, are in the valuable collection of Mr. Harcourt, of Stapleton. 
But the specimens which display the most vivid colouring, are 
those which are found near the river Moscorcica, about a league from 
Moscow. In one of these specimens, which I obtained from Mr. 
Heuland, the colours are not less splendid, nor less beautifully change- 
able, than those which the fire-marble itself displays, and are finely- 
disposed over the whole of the shell. In another specimen, either 
from France or from the neighbourhood of Moscow, the colour is the 
richest blue I have ever seen. 
Such of these shells as are found in schistose strata have generally 
suffered from compression ; as is mostly the case indeed, with all 
organic remains which have been thus preserved. This is particularly 
the case with the ammonites which are found atWatchett. In these spe- 
cimens, it often happens that the whole substance of a large shell is com- 
pressed into the thickness of a quarter of an inch. In ammonites which 
have been thus preserved, the shell is sometimes of a dead opaque 
white, whilst in others it reflects the most beautifully-coloured rays. 
The specimen represented Plate IX. Fig. 8, and which is, I believe, 
foreign, is very interesting, not only from its figure, but from its retain- 
ing a considerable portion of the original shell. Specimens of this 
kind are extremely rare ; for, in general, those which exhibit brilliant 
* Dr. Maton’s Tour to the Western Counties of England, Vol. I. p. 21. 
