a 
Sr 
Co 
AMMONITES falcatus. 
TAB. DLXXIX.—fig. 1. 
Spec. Cuar. Discoid, subumbilicate, radiated ; 
whorls crenated and flat at both edges, the in- 
ner ones almost concealed; radii falciform, 
bent in the middle; aperture sagittate with 
truncated angles. 
Syn. A. falcatus. Mantell Geol. Suss. p. 17. tab. 21. 
TO. a Le. 
EE 
“Tus rare and elegant species is almost flat, the long- 
est diameter exceeding its greatest thickness nearly four- 
fifths. 'The volutions are slightly enlarged in the centre, 
but are contracted at the ambit .... with delicate pli- 
cated edges. ‘The radii are very slender at their origin 
in the umbilicus, but gradually increase in breadth; and 
passing obliquely to the centre of the volutions, make a 
sudden curve towards the margin, where they terminate 
in obtuse folds.’’ The front is very narrow and flat; the 
cast of it shows a furrow along the middle in which the 
siphuncle was placed. 
_ Tam indebted to Mr. Mantell for permission to figure 
his best specimen, which was found at Middleham in 
Gray Chalk Marl. 
