79 



AMMONITES peramplus. 

 TAB. CCCLVII. 



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. 3IanteU, Fossils of the 

 South Doivns, 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 U 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 nx 

 diameter. When this Ammonite is laterally compressed 

 it approaches to the following. 



