PLATE X. 
1. Ammonites Planatus. ( Flattened Ammonite.) Discoidal, compressed; volutions four, inner ones about 
one-third inserted, flat as far as exposed, flattened on sides, and contracted by four or five varices ; inner half 
plain, outer with numerous, broad, slightly bent, regular, equidistant ribs, passing over back ; aperture oblong- 
oval. 
2. A. Sutheriandise. ( Sutherland's Ammonite.) Discoidal, gibbous, umbilicate; with two or three volu¬ 
tions, inner ones much inserted; umbilicus large, deep; sides smooth, plain; back very thick, regularly 
rounded ; length of aperture equal to about half diameter of shell. Diameter nearly 10 in. 
3. A. Selliguinous. ( Selliguinons Ammonite.) Discoidal, smooth; inner volutions few, almost wholly 
inserted, outer one enlarging rapidly; external margin or ambit obtuse; aperture very narrow, forming 
elongated ellipsis, sagittate wing to indentation of volution. 
4. A. Cinctus. ( Girdled Ammonite.) Discoidal, sub-umbilicate ; volutions three, depressed, three-fourths 
inserted, with transverse, annular, bifurcate, undulated ribs; umbilicus expanded, with marginal zone of 
oblique tubercles; ambit convex, embraced by ribs ; aperture ovato-sagittate. 
5. A. Catillus. ( Porringer Ammonite.) Discoidal, much compressed; three or four volutions, two-thirds 
concealed, thin inner margin narrow, obtuse; sides even, with row of short tubercles on each side of margin; 
aperture lanceolate-sagittate, with obtuse angles. Greatest diameter, G in.; thickness, not quite 1 in. 
6. A. Murchisonse. ( Murchison's Ammonite.) Discoidal, carinated ; with six or seven compressed volu¬ 
tions, with obtusely truncated inner edges, producing concave surface; inner ones two-thirds concealed : sides 
with obtuse undulations, bifurcating towards rounded ambit; aperture semi-elliptical; keel slightly pro¬ 
truding, containing siphunculus. 
7. 8, 9. A. Spinosus. ( Spined Ammonite.) Discoidal; four volutions, inner ones exposed, with many 
sharp, forked ribs, almost disappearing towards ambit; aperture sub-rotund. 
10, 11. A. Denarius. ( Denier Ammonite.) Discoidal, compressed; with four partly exposed volutions, 
flattened on edge, and with row of ten or twelve conical, obtuse tubercles on each side, all united to two 
ribs, with usually a third rib between ; in all, about thirty arcuated ribs, terminating abruptly near back ; 
aperture oblong. 
12. Vide PI. VIII., fig. 7. 
13. A. Brodiaei. ( Brodie's Ammonite.) Discoidal, gibbous, largely umbilicate; with seven nearly half- 
concealed volutions, with distant, transverse, strong ribs, from near edges of volutions, extending to centre, 
where they become very broad, with obtuse, nearly round tubercle, whence are numerous lesser, slightly 
curved ribs, passing over rounded ambit, meeting strong, tubercular ribs on opposite side; aperture curved, 
transversely oblong. Greatest diameter, nearly 4| in. 
14. 15. A. Humphriesianus. ( Humphries' Ammonite.) Discoidal, very thick; with five volutions, inner 
ones exposed; sides with large, numerous, distant ribs, extending to nearly centre of volutions, with large, 
oblong-ovate, conical tubercles, branching into three arcuated ribs, and passing over greatly rounded ambit, 
and meeting tubercles on opposite side; in inner volutions tubercles close to suture or line of separation; 
inner volutions much flatter on back than the others, producing quadrangular sections; aperture in young 
shell arcuated, oblong ; in the older shell semi-lunar. 
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