PLATE XIX. 
1. Ammonites Loscombi. ( Loscombe’s Ammonite.) Discoidal, compressed, umbilicate ; inner volutions con¬ 
cealed ‘ surface smooth, sides crossed by many, waved, flat ribs, with shallow interstices; back rounded ; aper¬ 
ture oblong; about two-fifths diameter of disc long ; thickness of shell one-tliird length of aperture. 
2. A. Geometricus. ( Geometrical Ammonite.) Discoidal, carinate, compressed; with five flat, almost wholly 
exposed volutions, crossed by many, sharp, straight ribs; back flattened, crenulated ; ambit, with small, narrow 
undulating carina; aperture narrow, oblong-oval. 
3. A. Constrictus. (Constrained Ammonite.) Discoidal, compressed, umbilicate; inner volutions concealed ; 
sides crossed by many, undulating, long and short ribs ; with row of acute tubercles on each side of margin of 
rounded ambit; aperture oblong, contracted by an obtusely edged lip; septa numerous, sinuated. 
4. A. Henslowi. (Henslow’s Ammonite.) Discoidal; with about four exposed volutions with flattened sides ; 
ambit rounded, with three, simple, slipper-shaped lobes on each side; lobes pointed inwards; intermediate 
saddles rounded outwards; sipliuncle situate on front edge in an acute lobe; aperture about four-fifths diameter 
of shell, double that in thickness. 
5. A. Artigyrus. (Perfectly Round-ribbed Ammonite.) Discoidal; with five, wholly-exposed, slightly- 
rounded volutions ; sides crossed by many, remote ribs; ambit rounded ; aperture sub-orbicular. 
6. A. Hawkserensis. (Hawkser’s Ammonite.) Discoidal, umbilicate, carinate, thick; with six, flattened, 
wholly exposed volutions, inner ones gradually thinner towards centre, forming deep umbilicus; crossed b 3 r 
strong, thick ribs, projecting over margin of flattened ambit; carina narrow, rounded, slightly elevated above 
surface ; aperture nearly quadrangular, corners rounded, and equal to about one-fourtli diameter of disc. 
7. A. Walcotii. (Walcot's Ammonite.) Discoidal, compressed, carinate ; with four, one-fourtli inserted volu¬ 
tions; on inner side of each a smooth concentric sulcus; external half of sides, crossed by many, semi-lunar ribs, 
about equal in breadth to intermediate sulci; on each side of carina a moderately deep groove; aperture oblong, 
length equal to one-third diameter of disc ; size, 2 in. to 4 in. 
8. A. Exaratus. (Ploughed Ammonite.) Discoidal, lenticular, umbilicate, carinate; with four volutions; 
inner ones almost wholly enveloped in outer one, visible only in small umbilicus; sides flattened, crossed by 
broad, flat, undulating ribs ; carina small, narrow. 
9. A. Lythensis. (Lyth Ammonite.) Discoidal, lenticular, umbilicate; with four volutions; inner ones 
wholly enveloped in outer one, and edges only seen in shallow umbilicus ; sides flat, crossed by many, flat, waved 
ribs; ambit thin ; aperture somewhat sagittate. 
ID. A. Rostratus. (Beaked Ammonite.) Compressed, carinate ; with about four, wholly exposed, flattened 
volutions; sides crossed by large, strong, remote ribs, each with three or four oblong tubercles; aperture ellip¬ 
tical, less than one-third diameter of disc, and at ambit terminating in slightly reflected, compressed beak ; 
tubercles confluent on outer volutions, but more distinctly divided on inner. Greatest diameter, 7£ in. 
11. A. Henleyii. (Henlejfs Ammonite.) Discoidal, with three or four wholly exposed volutions; sides 
crossed by many, flattened ribs, with large, compressed tubercles on reaching centre, whence they bifurcate and 
passing over ambit, produce crenulated margin to back; ribs also with tubercle near origin; between this 
and central row, volutions concave; aperture nearly orbicular, being two-fifths diameter of disc, with small 
sinus. Greatest diameter, 6 in. 
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