95 
AMMONITES Murchisonae. 
TAB. DL. 
Spec. Char. Discoid, carinated, when young* ra- 
diated ; whorls flattened, their inner edges ob- 
liquely truncated, the front rounded ; the inner 
whorls partly exposed; radii obtuse waved, 
usually forked, not passing on to the front. 
One of the many Ammonites that lose the rays or un- 
dulations as they increase in size ; and in which the 
innermost whorls, or those that probably existed in the 
egg, are also smooth : the radii are curved, irregular in 
their degree of elevation, and continue until the shell is 
about two inches in diameter, after which the whorls 
are almost suddenly plain, or only marked by lines of 
growth ; the truncature of the inner margin of the whorl 
produces a concave surface ; the form of the aperture is 
half an ellipsis, its sides are slightly projecting lobes ; 
the keel is very slightly prominent ; it contains, as usual, 
the siphuncle, which is strongly marked by the dark co- 
lour of the spar by which it is replaced. 
Broken out of a calcareous nodule composed of com- 
pacted Ammonites and other fossils, at the base of a cliff 
