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of the shell may have been removed by decomposition ; whilst the 
nacre, which has remained, in consequence of some peculiarity of struc- 
ture or of composition, assumes the appearance of being the real 
external shell. 
The nautilites of Shepey particularly engaged the attention of the 
late Mr. William Jones, who, speaking of those which are imbedded in 
septcii'ia, observes : “When this shell ( Nautilus ) is found lodged in the 
waxen vein, a phenomenon is observable in some of the specimens, 
which seems the most surprising and unaccountable of any that occurs 
in this branch of philosophy. The stone is quartered irregularly into 
tali or cubes, by seams of a coarse yellow spar, of the colour of bees- 
wax, which intersect the stone in many directions : and what is won- 
derful to see, these seams of spar pursue their course through the sub- 
stance of the nautilus, as if nothing had been interposed, though the 
shell is nearly as impenetrable as a flint. The case is very difficult, if 
we consider it as a penetration of the shell : but perhaps, when the shell 
was detained within the stone, it was obliged to part and crack, by the 
subsequent shrinking of the stone ; so that when the spar filled the 
seams of the stone, it filled up the crevices of the shell at the same time. 
The insinuation of the spar through the siphunculus, and its forming a 
column within the chambers of the shell, is another remarkable cir- 
cumstance. Upon the whole, the nautilus, thus inclosed, and affected 
by the waxen vein, is one of the most curious fossils in the world*.” 
In the neighbourhood of Whitby, situated on the sea-coast, in the 
North Riding of Yorkshire, a species of nautilites is found, which dif- 
fers from the preceding in the back part of the shell, or of its turns 
being flat instead of round : so that the sides go off almost at a right 
angle from the back of the shell. 
Between Bath and Bristol, in the neighbourhood of Keynsham, there 
is sometimes found another species, in which the back of the shell is 
* Physiological Disquisitions, &c. by William Jones, F. R.S. p. 392. 1781. 
