79 
AMMONITES peramplus. 
TAB. CCCLYII. 
Spec. Char. Discoid, with a few large obtuse 
radii ; whorls ventricose, the inner ones 
half exposed ; front rounded, plain ; aper- 
ture transversely obovate. 
Syn. A. peramplus. Mantell , Fossils of the 
South Downs , p . 200, 
Volutions four or five, almost half concealed and ra- 
pidly increasing in size, so that the last occupies one- 
third of the diameter of the shell : the aperture is but a 
little wider than long, but pressure has so much influ- 
ence upon this proportion, that it is not easy to determine 
the original form, some specimens perhaps being pressed 
in the opposite direction to others. The radii are most 
prominent at the inner part of each whorl, and are lost 
before they reach the front : there are about 14 upon the 
specimen before me : the crisped and deeply sinuated 
edges of the septa form an elegant ornament upon some 
parts of the surface of the specimen. 
Two or three large fragments and nearly perfect spe- 
cimens of this Ammonite, have been at various times 
presented to me by Gideon Mantell, Esq. who had ob- 
tained them in the neighbourhood of Lewes. The 
largest mass, as observed in a note to his description, 
p. 201, is part of a shell that was probably three feet in 
diameter. When this Ammonite is laterally coihpressed 
it approaches to the following. 
