169 
AMMONITES rotundus. 
TAB. CCXCHHEI. 
Fig. 3. 
Srec. Caar. Discoid; volutions exposed, costated: 
coste thick, numerous, split over the front : 
aperture orbicular. 
FE’ nom the small piece I possess of this I am not able 
to make a very full description, but there is enough to 
distinguish it from the last; the coste are less numerous, 
much thicker, shorter and not so regularly divided into 
two over the front, in a short fragment some are not 
divided others are split into three; the sides of the 
whorls are not compressed, on the contrary they are 
rather ventricose, so that the aperture is orbicular, ex- 
sept a small sinus produced by the preceding whorl. 
From Purbeck, probably found in the Kimmeridge 
Clay. 
AMMONITES decipiens. 
TAB—CCXCIV. 
Spec. Cuar. Discoid, depressed ; volutions ex- 
posed, costated ; coste large, obscure towards 
the front; front covered by numerous small 
ribs ; aperture oblong. 
FEF our or five volutions compose small specimens of this 
shell, they are compressed on the sides and round in 
frent; the numerous large coste are much elevated to- 
