10 
species also occurs in granular marly limestone, particularly 
at Craymouth, but seldom associated with the remains of any 
other species of shell. 
33. A. auritus,—T he Eared Ammonite, pi. VII. fig. 9* 
A. auritus . Sowerby, Min. Conch. II. p. 79, pi. 134; 
Mantel I, Geology of Sussex, p. 90 . 
Compressed, with four or five exposed volutions, the last 
one large, occupying about half the diameter of the shell ; 
surface covered with depressed, slightly developed, distant 
radiating ribs, every alternate one being furnished with a 
large obtuse tubercle, towards the inner margin of the volu¬ 
tions ; exterior margin deeply grooved, and provided with a 
series of large, obtuse, alternating, compressed tubercles, 
projecting in the form of ears ; aperture oblong-ovate, slightly 
sagittate. 
Discovered in the Micaceous Sand, in the bed of the canal 
at Devizes, Wiltshire, by Mr Gent; and it has subsequently 
been found at Ringmer in Sussex. 
34. A. splendens. — The Splendid Ammonite, pi. VII. 
fig. 10. 
Come (V Ammon fort plate, unie et ornee defleurs . Bour- 
quet Traite des Petrifactions, pi. 48, fig. 312. — Ammonites 
splendens . Sowerby, Min. Conch. II. p. I, pi. 103, figs. I, 2, 3; 
Mantell, Geology of Sussex, p. 89, pi. 21, figs. 13, and 17. 
Involute, compressed, provided with three or four volutions, 
the inner ones deeply inserted, being about three-fourths 
concealed, and the outer ones rapidly increasing in dimen¬ 
sions ; sides flattened, with transversely radiating, depressed, 
close ribs, slightly curved towards the aperture; a row of 
distant, greatly elongated tubercles towards the inner margin, 
from each of which two or three ribs emanate, and make an 
elegant curve from the inner to the outer margin, where they 
terminate in angular eminences, forming crenulated margins 
on the sides of the carina, the middle of which is nearly 
plain ; dissepiments sinuated and very foliaceous siphunculus 
situate near the inner margin ; aperture oblong, almost equal 
in length to half the diameter of the shell, and deeply indented 
by the inner volutions. Size varying from half an inch to 
two inches in diameter. 
This truly splendid Ammonite exhibits, on its external 
surface, the most beautiful iridescent play of colours, some¬ 
times equally vivid in lustre to the finest species of Haliotis , 
or Ear-shell. It is found in the Pyritaceous Marie at Folk- 
stone, Kent, and is common in the Blue Chalk Marie at 
Ringmer and Laughton, in Sussex. 
This species is often found with the shell remaining, which 
is extremely thin, and of a cream white colour. The folia¬ 
ceous sutures are very conspicuous in pyritaceous casts of 
this shell ; these differ but little from the fossil itself, except 
in the continuous structure, under the more prominent parts 
of the ribs, which are somewhat more depressed. Small 
specimens are sometimes found with the keel rounded, and 
the volutions nearly destitute of ribs, as exhibited in plate 
103, fig. 1, of Sowerby’s Mineral Conchology ; in this con¬ 
dition they might be mistaken for a distinct species. 
Mantell has figured a cast in Pyritous Marie, which shews 
the sinuous septa; small crystals of lime are contained in 
cavities on the opposite side of this specimen, and pseudo- 
morphous iron pyrites is disseminated through the mass. 
35. A. lautus. —The Laurel Ammonite, pi. VIII. fig. 1. 
Ammonites lautus. Parkinson, Geological Transactions, 
V. p. 58; Sowerby, Min. Conch. IV. p. 3, pi. 309, figs. 1, 2, 
Ammonites. 
3, 4, 5, and 6; Mantell, Geology of Sussex, p. 9, pi. 21, 
fig. 11. 
Discoidal, involute, compressed, with three or four two- 
thirds inserted volutions ; back narrow and deeply channeled ; 
sides furnished with numerous, strongly arcuated slender 
ribs, arising in pairs from a row of oblique, elongated 
tubercles near their inner margin, and being joined by 
alternating, intermediate shorter ones, proceed with an 
elegant curve to the outer margin, where they terminate, in 
somewhat depressed, large, alternating tubercles, usually 
three or four to each tubercle; these are disposed alternately, 
so that the edges may be characterized as serrato-tuberculate ; 
dissepiments very foliaceous; aperture obscurely sagittate, 
and equal in length to half the diameter of the shell. The 
situation of the siphunculus is unknown. 
Found at Laughton, Ringmer, and Norlington, Suffolk. 
Sowerby describes the following varieties of this fossil:— 
1 st 9 Ribs long, considerably arcuated and regular. Mineral 
Conch, pi. 319, figs. 1, 2. 
2r/, Having short irregular ribs provided with large 
tubercles near their inner ends. Min. Conch, pi. 319, fig. 6*. 
It is this variety which we have figured; the other varieties, 
if such they be, have not come under our observation. 
This species somewhat resembles the Ammonites dentaius, 
pi. 14, fig. 4, but the volutions are more exposed than in that 
fossil. It is also allied to Ammonites auritus , pi. 7, fig. 9, 
but is distinguished by its prominent and curved ribs, by 
the ridges on the inner volutions being less, two-thirds con¬ 
cealed, and by the centre one not being so tuberculous. 
36. A. armatus -The Armed Ammonite, pi. VIII. 
fig. 2. 
Ammonites armatus . Sowerby, Min. Conch. I. p. 215, 
pi. 95. 
Involute, with six or seven entirely exposed volutions, 
which are pressed against each other, and crossed by nume¬ 
rous annular ribs, each of which is provided with two series 
of large, short, furrowed spines, to the number of five on 
each ; the costag, after meeting on the point of the spines, are 
continued on the other side ; aperture obscurely four-sided ; 
siphuncle situate near the dorsal margin of the aperture. 
Found in the Alum Clay formation at Whitby, Yorkshire; 
the Oxford Clay, middle and south of England, and the Lias 
at Bath. 
In the young state, this shell is quite plain, without the 
slightest appearance of ribs or spines. In a more advanced 
condition, the ribs appear, and, when it lias acquired another 
convolution, the disk is flattened. 
This Ammonite is subject to considerable variety. 
37. A. planus. —The Flat Ammonite, pi. VIII. fig. 3. 
Ammonites planus. Mantell, Geology of Sussex, p. 90, 
pi. 21, fig. 3. 
Involute, carinated, compressed, deeply inserted, almost 
smooth; volutions crossed by nearly obsolete strise; keel 
flat, with its margin crenulated ; aperture sagittate ; dissepi¬ 
ments sinuate ; situation of the siphuncle is unknown. 
The inner volutions are three-fourths concealed, and the 
outer one consequently appears to increase very rapidly in 
dimensions, and is greatly larger than the others. 
This species is somewhat allied to Ammonites splendens , 
pi. VII. fig. 10, but may at once be distinguished in being 
destitute of tubercles on the inner margin of the volutions, 
and is also devoid of the radiations, which ornament the 
MOLLUSCA. 
