163 
AMMONITES rostratus. 
TAB. CLXXIIL. 
~Seec. Cuar. Depressed, carinated, tuberculated; 
tubercles three or four upon each radius, 
largest towards the front; volutions exposed ; 
aperture elliptical, with a compressed reflected 
beak. 
— 
Tue aperture, exclusive of the beak, is somewhat less 
than a third of the diameter of the shell long ; the beak 
is a little reflected and flattened, the edges of it so pressed 
together, as nearly to close it: the tubercles are more 
divided upon the inner whorls than upon the outer ones, 
where they begin to run into one another, and form 
ridges that are curved forwards, towards a prominent in- 
sulated keel : volutions about four. 
So remarkable is the beaked mouth of this Ammonite, 
that I have named it from that character. The figure is 
taken from a specimen lent me with a valuable collection 
of the same Genus by the Rev. Mr. Buckland; it was 
found in Chalk Marl at Roak Village, near Benson, Ox- 
fordshire. ‘The terminal chamber or that in which the 
animal is supposed to have resided, being preserved 
entire, renders the specimen particularly valuable, as it 
is commonly broken off. 
tL. FL XKK 
