PLATE IX. 
1. Ammonites Sowerbii. ( Sowerby's Ammonite .) Discoidal, carinated, with four volutions, inner ones 
half inserted or to base of tubercles, having a series of nine or ten spiriform tubercles in centre of each on obtuse 
ridges; inner half of volution smooth, outer half, with many slightly bending ribs, terminating at keel; keel 
defined, entire, projecting, greatly rounded externally, almost separated from volutions, with siphunculus situated 
in its outer extremity ; aperture elliptical. 
2. A. Koenigi. ( Koenig's Ammonite.) Discoidal, convex, with six volutions; inner ones half inserted; 
sides with distant, strong ribs, like oblong tubercles, commencing at inner margins of volutions and extending to 
about the centre, met by many slightly arcuated, gently raised ribs extending over rounded ambit; aperture 
cordiform, elongated ; septa few, with sinuated lobes. 
3. 6. A. Listeri. ( Lister’s Ammonite .) Sub-discoidal, thickness nearly equal to diameter, with five or six 
narrow volutions; inner ones partly inserted and deeply sunk; back or ambit very convex, broad ; sides 
inversely conical, with numerous strong, sharp ribs extending over the ambit, and meeting on opposite side, 
terminating in a series of strong, elevated, pointed tubercles on inner margin of volutions. Diameter 14 in. to 2 in. 
4. A. Discus. ( Quoit Ammonite.) Discoidal, umbilical, much compressed, volutions smooth, much con¬ 
cealed ; outer margin acuminated ; aperture sagittate, occupying half diameter of disc and one-sixth in breadth ; 
septa irregularly undulated ; aperture sagittate. Greatest diameter 4 in., thickness 4 in. 
B, 10. A. Strangewaysii. ( Strangeicay's Ammonite.) Discoidal, carinated, with five volutions, with sides 
nearly flat; obscure concentric furrow, the margin of outer one flattened, slanting from centre and inner edges 
of others obliquely depressed ; the whole crossed by numerous, slightly raised, twice curved, undulating ribs, 
being frequently obscure on inner side and centre of volutions, but larger on dorsal edge; each rib forms 
two semicircles reversed to one another; aperture oblong, occupying nearly one-third of diameter of disc. 
Greatest diameter about 6 in. 
7, 8. A. Greenovii. ( Greenough’s Ammonite.) Discoidal, compressed ; volutions four or five, two-thirds 
inserted, outer one being nearly half diameter of shell; obscure ribs most apparent towards rounded back, over 
which they pass ; those on inner volutions quite distinct; aperture elliptical, with deep indentation from inser¬ 
tion of volution ; siphunculus placed near centre of back margin of aperture ; septa close, greatly sinuated, locked 
into each other at margins. Greatest diameter 12 in. to 20 in. 
9. A. Vertebralis. ( Jointed Ammonite.) Discoidal, carinated; five volutions, inner one partly inserted; 
sides, with numerous prominent, slightly undulating ribs, tuberculate in centre, whence they bifurcate, each 
branch having acute, compressed tubercle near centre, whence branches curve towards keel, where another 
slightly reflected tubercle is produced and branches re-unite on opposite side ; keel serrato-tuberculate, resembling 
somewhat the vertebral column in mammalia ; aperture ten-sided. 
11. A. Concavus. ( Concave Ammonite.) Discoidal, involute, compressed, carinated, umbilicate ; with four 
exposed volutions, concave near centre, crossed by numerous curved, unequally long ribs; keel sharp, entire; 
aperture half diameter of disc, acutely triangular; external angle sub-rotund, with interior angles obliquely 
truncated. 
12. A. Bechei. (De la Beetle's Ammonite.) Gibbous, umbilicate; inner volutions entirely concealed, sides 
very prominent, with many nearly straight, transverse ribs, crossed by many close, elevated, concentric strise ; 
each side with two rows of many small, depressed tubercles; aperture large, as wide as long, occupying half 
diameter of shell. 
13. A. Elegans. ( Elegant Ammonite.) Discoidal, involute, with very acute, entire keel, within which a 
small siphunculus, with three to four volutions, inner ones about two-thirds inserted, with many equal, doubly 
curved ribs; aperture acutely triangular, occupying two-thirds of disk ; internal angles truncate ; thickness of 
shell about one-third its diameter; septa rather close, with sinuous, plaited margins. 
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