1 
AMMONITES Parkinsoni. 
TAB. CCCVI.L 
Spec. Char. Discoid, with numerous highly ele- 
vated radii ; whorls numerous, the inner ones 
exposed ; radii slightly arched, bilid near the 
front which is very narrow and plain. 
V olution s numerous, with slightly convex sides and 
narrow edges : the arched radii are bent forward at 
their outer ends, and nearly meet at an acute angle 
upon the front, but do not pass over it : the edge of the 
shell is nearly flat, in the cast it is hollow in conse- 
quence of the removal of the siph uncle ; the aperture is 
oblong, narrowest towards the front. 
This is the Ammonite so frequently split, polished, 
and sold at Bath : its outer surface is also often ground 
and polished, shewing ramifying, sinuated, or simply 
undulated edges to the septa, according to the depth to 
which it has been worked. Misled by worked specimens 
that had lost the flat space in the middle of the edge, 
I have erroneously referred this species to the Am. gi° 
ganteus, at page 55 of Vol. I. while speaking of such 
as are found near Keynsham, and those fine specimens 
given me by Dr, Lettsom, all of which are flatter than 
even the variety a of the giganteus, and have more 
whorls. The species before us occurs chiefly in Lyas, 
a stratum not known to contain any silicious deposit ; 
it is consequently never imbedded ip Chert or Flint, 
like the A. giganteus I suspect it also may be found 
Vol. IV. 
