7 6 
AMMONITES rotiformis. 
TAB. CCCCLIII. 
Spec. Char. Depressed, ribbed, carinated, a 
furrow upon each side of the keel ; inner 
whorls exposed, many; ribs many, strong, 
each terminating in a tubercle; aperture 
nearly square. 
The sides of this Ammonite are very slightly concave, 
the front is flat with a sunk keel; the ribs rising in knobs 
just as they reach the front, give the whorls a very 
square aspect ; the ribs and the hollows between them, 
are nearly equal ; the aperture occupies only one sixth 
of the diameter of the shell, and is very little longer 
than wide. 
From the Lyas, near Yeovil; the specimen is very 
rugged, about seven inches in diameter; the figure is di- 
minished. 
AMMON ITES mul^costata. 
TAB. CCCCLIV. 
Spec. Char. Depressed, costated, carinated, a 
furrow on each side of the keel ; inner 
whorls exposed, few ; ribs strong, sharp, 
numerous, with a tubercle near the end of 
each ; aperture oblong. 
Much resembling the last, but not so flat ; the ribs dif- 
fer jn fojm ; they are more extended over the front and 
bent forwards from the depressed tubercle nearly to the 
furrow ; the length of thp aperture is more than one 
fourth of the diameter of the last whorl ; the sides are 
not so remarkably flat, as in the A. rotiformis. 
The figure is diminished from an individual 14 inches 
in diameter, and between 3 and 4 inches thick, found in 
Lyas near Bath. 
