119 
AMMONITES Mantelli. 
TAB. LV. 
Spec. Cuar. Depressed, edge three-sided, broad, 
and flattish ; sides flattish ; volutions undulated, 
about two-thirds concealed, undulations alter- 
nately reaching across the whorl. 
rer 
Tur aperture equals about two-fifths of the diameter, 
which is often four inches, and the thickness about one. 
The outer edges of the septa have five principal folds. 
The shorter undulations of the surface reach about two- 
thirds over the whorl. Aperture obscurely six-sided, one 
side embracing the next whorl. Whorls three or four. 
I am favoured by the indefatigable G. A. Mantell, Esq. 
with numerous specimens of this species from Ringmer, 
east of Lewes in Sussex. Good specimens seem to be 
scarce, and as I had not seen such distinct ones before, I 
indulge myself in laying before the public the older and 
younger shell. I have also commemorated my friend in 
the specific name. The substance is a coarse buff-coloured 
marly limestone with a few ochraceous stains. I presume 
the species may sometimes be much larger, and then 
perhaps the characters may be more obliterated, as appears 
to be the case in the larger of these. I-believe it sometimes 
varies a little, and has more prominent or knotted joints 
to the costa and somewhat diversified*. I suppose the 
siphunculus to be in the outer edge of the septa. 
* Of this variety I have lately received a very large specimen from 
Hamsey near Lewes, by favour of the same Gentleman, 
