25 
AMMONITES rhotomagensis. 
TAB. DXV. 
Spec. Char. Discoid, radiated, umbilicated ; inner 
whorls partly concealed ; radii about 20, fur- 
nished with three short tubercles upon the 
front, and two more or less elevated upon each 
side ; whorls thick, with flattish sides ; aper- 
ture oblong. 
Syn. Am. rhotomagensis. Cuv. $$Brongn. Env. de 
Paris , p. 83. t. 6./. 2. 
Am. sussexiensis. Mantell , Geol. of Sussex, 
p. 114. t. 20. f. 2. and t.Ql.fig. 10. 
In the centre of the rounded front of this Ammonite 
is a row of tubercles, one placed upon each rib ; on 
each side of this is another similar row : these, toge- 
ther with the flattened sides and wide umbilicus, are 
the distinguishing characters ; the other two rows of 
tubercles are very variable, the outer one often ri- 
sing into obtuse spines. When these tubercles are in- 
conspicuous, it bears a strong resemblance to A. Man- 
