3 
AMMONITES dentatus, 
TAB, CCCVIII. 
Spec. Char. Discoid, urn bili cate, radiated ; front 
square* ; radii prominent and forked near 
their commencement, terminating upon the 
edges of the front. 
Syn. Am. serratus, Parkinson in Trans „ QeoL 
Soc. V. 57. 
A lthough this shell may be described as umbilicated, 
the inner whorls are in part exposed : the radii are 
slightly curved ; they are most prominent at a short 
distance from their commencement, where also they are 
forked ; each branch is slightly enlarged and bent 
forward upon the edge of the front, where it ends : thus 
the front has two serrated edges, the intermediate space 
being plain : the aperture occupies about two-fifths of 
the diameter of the shell in length, and is one-fourth 
in width. 
This appears to be A. serratus of Parkinson ; but as 
it is totally different from the Ammonite, to which that 
name had been previously giyen at tab, *24 of this work, 
it has become necessary to change it. 
AMMONITES” lautus. 
TAB. CCCIX. 
Spec. Char. Discoid, radiated ; inner whorls half 
concealed ; front narrow, slightly concave ; 
principal radii slender, varicose, or tubercu- 
lated near their commencement ; shorter radii 
alternating, united in pairs to form compressed 
tubercles upon the edges of the front, 
Syn. Am. lautus, Parkinson in Trans . GeoL 
Soc . V. 58. 
var. a, radii long, elegantly arched, and regular. 
var. /3, radii short, irregular, with strong tuber- 
cles near their commencement. 
The inner whorls are more exposed in this than in the 
last, and the sides of the whorls generally more convex, 
especially in a : in var. ,3 the lesser radii are often joined 
at the tubercles to the larger ones * the form of the 
aperture approaches to elliptical. 
Figures I and 2 are from var. oc. and fig. 6 var. (3 ; 
* The siphuncls is sometimes decomposed away, and leaves a hollow 
that may deceive. 
