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AMMONITES latecosta. 
TAB. DLVI.—fig. 1. 
Spec. Cuar. Discoid, compressed, radiated ; whorls 
5, exposed ; radii large, sharp, slightly waved, 
much flattened and widened as they pass over 
the rounded front ; aperture oblong. 
Tue flattened sides of this Ammonite distinguish it 
from the young state of A. planicosta (tabs. 73 and 406), 
independently of its much larger size. When young, nei- 
ther of them has any appearance of spines; when old, the 
last whorl of the latecosta has only slight indications 
of tubercles, which consist of two small knots upon each 
ray on each side; the planicosta has one large spine in 
place of two, and that only upon some of the rays. 
A Lyas-fossil: all-the specimens I have seen except 
one are from Alluvium; that one is from Lyme: it is 
about 34 inches in diameter, and was liberally presented 
by Mrs. Murchison. One specimen nearly four inches in 
diameter shows the little knots upon the rays; it is in the 
collection of W. Peete, Esq. of Dartford. Several small 
ones have been found by Miss Baker at Braunston, in 
what is called a gravel-pit. 
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AMMONITES brevispina. 
TAB. DLVI.—fg. 2. 
Spec. Cuar. Discoid, compressed, radiated ; whorls 
5 or 6; inner ones exposed ; rays numerous, 
passing over the round front, furnished with 
2 small spines on each side ; aperture obovate. 
Tue rays are rather blunt, and not much elevated, but 
most prominent where they pass over the front. The 
spines are short, and placed near the inner and outer 
si of the whorls. 
ragments of this Ammonite were brought from 
Pabba last year, by R. I. Murchison, Esq. 
