149 
AMMONITES plicatilis. 
TAB. CLXVL 
Spec. Char. Discoid, radiated ; sides flat ; front 
rounds plain in the centre ; volutions exposed; 
radii numerous, equal, straight, furcate ; 
aperture squarish, with rounded angles. 
The radii oh this Ammonite, from their straightness, 
closeness, and regularity, have much the appearance of 
artificial plaiting or crimping ; they do not branch until 
they begin to turn over the front, in the centre of which 
they are nearly obliterated; they are sometimes simple 
and less frequently trifid. The septa are acutely si- 
nuated. The thickness is about one-fourth the diameter : 
the aperture is somewhat longer than wide. 
A sandy Stratum, containing beds of sandy Limestone, 
at Dry Sandford and Marcham, N. W. of Abingdon, pro- 
duces this shell ; I am indebted for the use of the speci- 
men figured, to the Rev. William Buckland. Several 
other Ammonites occur in the same Stratum, among 
them is A. concavus of tab. 105*: most of them have 
lost the shell ; the present is only a cast of the inside, it 
has a few crystals of Carbonate of Lime about it. 
* The inside casts of this are so well preserved, with regard to the sinu- 
osities, that 1 wets almost induced to add a fresh figure of it from some 
elegant specimens lent me by the Rev. W. Buckland. 
