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cum stance that renders it more distinct from A. peramplus 
than otherwise it would appear. I have an intermediate 
specimen from Dover, by favour of Mr. Sankey, the 
aperture of which is elliptical ; and a small one from 
Lewes, between the two ; both these have the radii 
distinct, especially the small one, in which they extend 
nearly to the front : these specimens lead me to suspect 
the A. Lewesiensis is only a compressed variety of the 
peramplus. Mr. Phillips has observed in his paper on 
the Chalk Cliffs near Dover, (Trans. Geol. Soc. V. 
p. 30 and 33), that the Ammonites lie horizontally in the 
Chalk : this may account for their being so frequently 
compressed : but as Mr. Mantell has had numerous 
opportunities of observing them, I have followed him in 
describing them as two species. I have seen one on the 
beach near Dover that measured full three feet across, 
but it is so long ago that I do not know which species to 
refer it to. 
