Ammonites. 
MOLLUSCA. 
surface of the former species. It is, however, like that shell, 
frequently iridescent on the surface. 
Found at Kingmcr, by G. Mantell, Esq. 
38. A. cordatus _The Cordate Ammonite, pi. VIII. 
fig. 4. 
Ammonites cordatus. Sowerby, Min. Conch. I. p. 51, 
pi. 17, figs. 2 and 4. 
Involute, carinated; volutions four or five, somewhat 
compressed, inner ones half inserted; sides ornamented with 
undulating ribs, extending over the inner half of each volu¬ 
tion ; the remaining half provided with about five divergent 
undulations to every two ribs, all of which terminate in the 
exterior crenated margin ; aperture cordiform, two-thirds of 
the diameter of the shell in length. Diameter varying 
from one to two inches; thickness about a third of its 
diameter. 
Found in the Limestone of Shotover, Oxfordshire, and 
also in Somersetshire. 
39. A. Browni—B rown’s Ammonite, pi. VIII. fig. 5. 
Ammonites Browni. Sowerby, Min. Conch. III. p. 114, 
pi. 163, figs. 4, 5. 
Discoidal, carinated; five half inserted volutions, with 
a zone of large distant tubercles placed towards the centre 
of the volutions, but rather nearest the inner sides ; these 
assume the form of ribs on the outer volutions ; from the 
tubercles, the other half of the volutions are provided with 
numerous equidistant, somewhat curving ribs, which extend 
over the rounded ambit; aperture cordiform. 
Found at Dandry, by G. W. Braikenridge, Esq. and 
named in honour of Robert Brown, Esq. the celebrated 
botanist. 
This species has much the appearance of Ammonites 
Kcenigi , pi. IX. fig. 2.; but the keel and tubercles upon the 
inner volutions sufficiently distinguish it from that shell. 
40. A. a nnulatus. — The Ringed Ammonite, pi. VIII. 
fig. 6. 
Ammonites annulatus . Sowerby, Min. Conch. III. p. 41, 
pi. 222. 
Discoidal, with from five to seven exposed volutions, 
crossed by numerous, close, very prominent ribs, which are 
frequently bifurcated as they pass over the rounded ambit; 
aperture subrotund. 
Found at Whitby, Yorkshire; in the lower sand beds of 
the inferior Oolite at Cropredy, near Bunbury, Oxfordshire, 
and also near 11 minster. 
This species, at first appearance, has somewhat the aspect 
of Ammonites communis , pi. VI. fig. 9.; but its numerous 
ribs sufficiently distinguish it, and, besides, it has more volu¬ 
tions. The ribs are placed very near each other, and a deep 
furrow is formed between them; some being bifurcate as 
they pass over the ambit. Sowerby says, “ When the outer 
surface of the shell,—which adheres strongly to the stone,—is 
broken oft', the ridges are much diminished ; and, instead of 
convex surfaces, like wire wound about the shell, they are 
fiat, as if they were formed of square wire. The cast, when 
all the shell is removed from it, is also marked by slightly 
elevated radii.” 
In some specimens, the sides of the volutions are somewhat 
compressed ; in others, they are a little inflated ; in these 
separate conditions, they look considerably different, but 
may be at once recognized by the numerous strong annu- 
lations. 
11 
41. A. curvatus. — The Bending Ammonite, pi. VIII. 
fig. 7, and pi. X. fig. 12. 
Amtnonites curvatus. Mantell, Geology of Sussex, p. 118, 
pi. 21, fig. 8.; Sowerby, Min. Conch. VI. p. 154, pi. 179? 
fig. 2. 
Discoidal, carinated, compressed, subumbilicate, with three 
deeply inserted volutions, which are ornamented by trans¬ 
verse, falciform, numerous ribs ; these are bifurcated at their 
commencement, and terminate in broad, curved, tubercular 
costae ; keel with a longitudinal sulcus, situate between two 
marginal series of tubercles ; ambit fiat and narrow ; umbi¬ 
licus large, aperture obtusely sagittate; siphuncle situate in 
the dorsal furrow. 
This species is nearly allied to the following, but appears 
quite distinct. Mantell says, “ The curvatures are more 
numerous in the Ammonites falcatus than the oblique radii; but, 
in the present species, the proportions are reversed, two or 
three radii uniting to form one curved rib. The terminations 
of the ribs in the latter are tubercular, and separated from 
each other by a sulcus ; in the former, they are gently curved, 
and appear as if folded or plaited over each other.” 
The umbilicus is somewhat deeper than in Ammonites fal¬ 
catus, and is provided with a row of oblique tubercular pro¬ 
cesses, from each of which two or three ribs emanate, and 
continue to the centre of the volutions, where they unite, to 
form a broad curved rib, that terminates in an oblong-ovate 
tubercle on the margins of the ambits. Another tubercle is 
situate on the middle of the curved parts. The keel is 
grooved, and has two belts of prominent, distinct opposite 
tubercles formed by the terminations of the ribs. 
Discovered at Ilamsey by Mr Mantell. 
42. A. falcatus. — The Ilooked-ribbed Ammonite, 
pi. VIII. fig. 8. 
Ammonites falcatus. Mantell, Geology of Sussex, p. 117, 
pi. 21, figs. 6 and 12; Sowerby r , Min. Conch. VI. p. 153, 
pi. 579, fig. 1. 
Discoidal, carinated, greatly compressed, subumbilicate; 
with three deeply inserted volutions, Hat on both edges; 
sides furnished with numerous close, plicated, falciform ribs, 
extending a little way down the sides of the umbilicus, which 
is small, and with crenulated margins ; ambit Hat, narrow, 
and provided with a longitudinal sulcus; margin plicated; 
aperture sagittate ; siphuncle placed in the furrow, which is 
in the centre of the dorsum. 
This handsome species is nearly flat, its longest diameter 
exceeding its greatest thickness almost four-fifths ; the sides 
are slightly inflated in the centre, but are contracted at the 
ambit into a narrow flattened carina, with a sulcus in its 
centre, and with the edges slightly plicated; the ribs are 
extremely slender at their origin in the umbilicus, but gra¬ 
dually increase in breadth as they approach the centre of the 
volutions, where they become suddenly curved, and sweep 
elegantly towards the dorsal margin, where they terminate in 
obtuse folds. 
Found at Middleham and Stonehaven, Sussex, in the Gray 
Chalk Marie. 
43. A. Brocchii.—B rocchi’s Ammonite, pi. VIII. fig. 9* 
Ammonites Brocchii. Sowerby, Min. Conch. II. p. 233, 
pi. 202. 
Compressed, with three or four greatly rounded volutions; 
the inner ones half concealed ; sides hollow ; ambit circular ; 
a row of oblong-ovate ribs commence near the inner margin 
