PLATE XV. 
1. Ammonites Bennetianus. ( Bennet's Ammonite.) Sub-globose, with four to six rapidly increasing volu¬ 
tions, inner ones partly concealed, with row of nine or ten large, conical, blunted tubercles on each side, and a 
series of twenty very large obtuse tubercles on each side of back or ambit, connected by prominent, obtusely 
rounded ribs ; aperture transversely oblong. 
2. A. Tetramraatus. ( Four-tubercled Ammonite.) Discoidal, carinated ; with four or five convex volutions 
crossed by numerous obscure, furcated ribs, each with four round, blunt tubercles, external ones compressed, and 
two on the shorter branches; carina sharp, entire. 
3. A. Vernoni. (Vernon's Ammonite.) Discoidal, with three or four rounded volutions, inner ones nearly 
half inserted ; sides with numerous elevated, furcated ribs, from inner sides of volutions bifurcating at centre, 
thence passing over rounded back adjoining those of opposite side; aperture oblong. 
4. A. Williamsoni. ( Williamson's Ammonite.) With five or six thick, slightly raised volutions, inner ones 
wholly exposed; sides crossed by many straight, elevated, parallel ribs from inner margin of volutions, passing 
over broad, flat, thick ambit to inner margin of volutions on opposite side ; aperture oblong, nearly quadrangular. 
5. A. Vittatus. (. Filleted Ammonite.) Discoidal, carinated ; with four or five slightly raised volutions, inner 
ones one-third inserted; sides crossed by many straight, slightly elevated ribs terminating on the side of 
sharp, thin, elevated carina; every rib with two tubercles, one at each end. 
6. A. Gowerianus. ( Gower's Ammonite.) Compressed, deeply umbilicate; with six or seven convex volu¬ 
tions, inner ones half inserted, deeply sunk below level of outer one ; sides crossed by many elevated sharp ribs, 
with a large, sharp, elevated spine, at outer extremity of which, ribs separate into three or more obtuse, annulate 
ridges, passing over rounded back or ambit; aperture oblong, equal to nearly one-third diameter of shell; edge 
thin, slightly sinuated near inner termination. 
7. A. Navicularis. {Little Ship Ammonite.) Umbilicate, with three to four narrow, compressed, deeply 
inserted, ventricose volutions, with a numerous series of strong, smooth elevated, annulose, transverse ribs from 
inner margin of volutions, passing over large rounded ambit to inner margin on opposite side of volutions ; ribs 
and intervening sulci of nearly equal breadth ; aperture transversely oblong. Greatest diameter, 7 in. 
8. A. Crenularis. {Crenulated Ammonite.) Lenticular, umbilicate, with five inflated volutions, inner ones 
three-fourths inserted, central three deeply sunk; sides crossed by strong, elevated, remote, curved ribs, which, 
on reaching centre, are met by many smaller ribs passing over sharp ambit, producing crenulated, subcarinated 
back ; aperture large, somewhat cordiform. 
9. A. Complanatus. {Levelled Ammonite.) Lenticular, very flat, umbilicate ; volutions entirely concealed, 
thickest in centre of shell; ambit protruded into narrow, slightly convex, crenated carina, produced by angular 
terminations of plicae; inner half of disc, with transverse, undulating striae; outer portion plicated ; aperture 
slightly sagittate, not more than one-fifth of an inch wide ; keel, with elevation and ridge down centre. Greatest 
thickness one-eighth inch ; umbilicus very small; septa numerous, very foliaceous. Greatest diameter, 8 in. 
10. A. Undatus. {Waved Ammonite.) Discoidal, much compressed, smooth, with three flat volutions, 
central ones partly visible, and inner margins of whole square; ambit slightly rounded ; sides, with remote 
undulations, passing over back; aperture sagittate, greatly elongated, with obtuse angles. 
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