51 
AMMONITES acutus. 
TAB. XVII .—Fig. 1. 
Spec. Char. Involute, rather depressed, inner turns 
half exposed, surface with straight projecting 
radii extending over the interior half of each 
whorle; margin crenated. Aperture triangu- 
larly cordate, two-fifths of the diameter of the 
shell in length. Volutions three or four. 
Shell about one inch in diameter, and one-third of an inch 
thick, slightly carinated, flatfish at the edge, with about 
three crenatures to each of the radii. 
This is from the cliff near Minster on the Isle of Sheepy, 
it is a cast in blackish Pyrites, but after some years has 
luckily not begun to decompose, and still looks neat and 
• elegant. On some parts the calcareous shell remains of a 
dull brown colour. The mouth is filled with little tuberose 
accretions of Pyrites, giving it the appearance of the mouth 
of a cornucopia. 
AMMONITES cordatus. 
TAB, XVII .- — Figures 2 and 4. 
Spec. Char. Involute, rather depressed, carinated’, 
inner turns half exposed; surface with angular, 
projecting, undulating radii, extending over the 
inner half of each whorle, the remaining half 
covered by diverging undulations terminating 
in a crenated margin. Aperture cordate, two- 
fifths of the diameter of the shell long. Volu- 
tions four or five. 
From one to two inches in diameter, and about one-third 
of its diameter in thickness; generally about five external 
undulations to two radii; no depression upon the edge. 
The specimen, figure 2, shows the exterior surface of the 
