136 
AMMONITES Rotula. 
TAB. DLXX.— jig. 4. 
Spec. Char. Gibbose, smooth, umbilicated ; each 
whorl contracted by six or seven varices ; inner 
whorls partly exposed ; front rounded, crossed 
by many small furrows ; aperture orbicular. 
Whorls very few. 
In this species of Montfort’s genus Planulites the con- 
tractions of the whorls are very conspicuous. Their num- 
ber is various ; some specimens having seven or even 
eight in each whorl : they are perfectly independent of 
the septa. 
Casts in Pyrites collected at Speeton on the coast of 
Yorkshire. 
AMMONITES planulatus. 
TAB. DL XX.— jig. 5. 
Spec. Char. Depressed ; whorls flat on their sides, 
contracted by four or five varices ; inner whorls 
two-thirds exposed ; front crossed by many 
broad furrows ; aperture oblong oval. 
Half of each whorl is plain, the remaining part mark- 
ed with numerous broad furrows that pass over the 
rounded front ; the inner edges of the whorls are ob- 
tuse, the exposed portion of the inner whorls is flat. 
A single specimen found in the Marl at Hamsey, near 
Lewes, is in the collection of Mr. Mantell, who has 
kindly permitted it to be engraved. 
