Ammonites. 
MOLLUSCA. 
13 
each other at their margins. Greatest diameter varying from 
twelve to eighteen and even twenty inches. 
Found in the Lias, in the middle and south of England, 
and also in the Lias at Lyme Regis. 
In the larger specimens there is no appearance of ribs, but 
sometimes with a few very remote, slightly indented, diver¬ 
gent furrows, such as we have represented. This beautiful 
species is frequently formed of pyrites, and exhibits on its 
surface the most splendid iridescent play of colours. 
This species was named by Sowerby in honour of the cele¬ 
brated and munificent geologist, J. B. Grecnough, Esq. of 
London. 
51. A. vertebralis. —The Jointed Ammonite, pi. IX. 
fig. 9- 
Ammonites vcrtcbralis , Sowerby, Min. Conch. II. p. 147? 
pi. 165, figs. 1, 2. 
Discoidal, carinated, five volutions, the inner ones partly 
inserted ; sides furnished with numerous prominent, slightly 
undulating ribs, which are tuberculate in the centre, from 
whence they are regularly bifurcate, each branch being pro¬ 
vided with a somewhat acute, compressed tubercle near its 
middle, from whence the branches curve towards the keel, 
where, at their termination, another slightly reflected tubercle 
is produced, and the branches reunite on the opposite side ; 
keel serrato-tuberculate, resembling in some measure the 
vertebral column in mammalia; aperture ten-sided. 
Found in the beds of Siliceous sand at Dry Sandford and 
Marsham, near Abingdon, Berkshire. 
52. A. concavus. —The Concave Ammonite, pi. IX. fig. 11. 
Ammonites concavus , Sowerby, Min. Conch. I. p. 214, pi. 
94, lower figure. 
Discoidal, involute, compressed, carinated, umbilicate ; with 
four exposed volutions, concave near the centre, crossed by 
numerous, curved, unequally long ribs, which are less distinct 
towards their centre; keel sharp, entire ; aperture half the 
diameter of the disk, acutely triangular ; external angle sub¬ 
rotund, with the interior angles obliquely truncated. 
Found at Ilminster. 
53. A. Bechei. —De La Beche’s Ammonite, pi. IX. fig. 12. 
Ammonites Bechei , Sowerby, Min. Conch. III. p. 143, pi. 
280, figs. 1, 2. 
Gibbous, umbilicate ; inner volutions entirely concealed ; 
sides very prominent, with numerous nearly straight trans¬ 
verse ribs, about two to each tubercle, which are less deve¬ 
loped towards the centre, but increase in strength as they 
approach the much rounded ambit, over which they pass con¬ 
tinuously ; these are crossed by many close, elevated, con¬ 
centric strise ; each side provided with two rows of numerous, 
small, slightly depressed tubercles, those of the inner row 
most prominent; between these rows the sides are a little 
flattened ; aperture large, as wide as it is long, occupying 
half the diameter of the shell. 
Found in the Blue Lias at Lyme Regis, Dorsetshire. 
54. A. e leg a ns. —The Elegant Ammonite, pi. IX. fig. 13. 
Ammonites elegans , Sowerby, Min. Conch. I. p. 213, pi. 94, 
—upper figure. 
Discoidal, involute, with a very acute entire keel, within 
which the small sipliuncle is placed ; three to four volutions, 
much compressed on the sides, the inner ones about two- 
thirds inserted ; furnished with numerous, equal, doubly 
curved ribs ; aperture acutely triangular, occupying about 
two-thirds of the disk ; internal angles truncate ; thickness of 
the shell about one-third its diameter; septa rather close, 
with their margins sinuous and greatly plaited. 
Discovered between Ilminster and Yeovil by Mr Strange- 
ways. 
55. A. planulatus. — The Flattened Ammonite, pi. X. 
fig. 1. 
Ammonites planulatus. Sowerby, Min. Conch. VI. p. 136, 
pi. 570, fig. 5. 
Discoidal, compressed ; volutions four, inner ones about 
one-third inserted, and flat as far as is exposed, flattened on 
the sides, and contracted by four or five varices, the whole 
with their inner half plain, the other having numerous, broad, 
slightly bent, regular, equidistant ribs, passing over the back, 
which is much rounded ; aperture oblong-oval. 
Found by G. Mantell, Esq. in a Marie pit at Hamsey, near 
Lewes. 
56. A. Sutherland i a:.—S utherland’s Ammonite, pi. X. 
fig. 2. 
Ammonites Slither landice. Marchison, Geological Trans¬ 
actions, 2d Series, II. pt. 2, p. 323; Sowerby, Min. Conch. 
VI. p. 121, pi. 563, figs. 1, 2. 
Discoidal, gibbous, umbilicate ; two or three volutions, 
inner ones much inserted ; and only partly seen within the 
large and deep umbilicus ; sides smooth and plain ; back very 
thick, and regularly rounded ; length of the aperture about 
equal to half the diameter of the shell, which is nearly ten 
inches. 
Discovered by R. I. Murchison, Esq. in the White sand¬ 
stone at Braambury Ilill, Brora, Sutherlandshire, and in the 
Coral Oolite and Calcareous grit of Yorkshire. 
Named in honour of the Duchess Countess of Sutherland. 
There is a remarkable specimen in the Collection of the 
Geological Society, which was found by the quarrymen, and 
presented to the late Duke of Sutherland. It was supposed 
to have been a fossil human skull; it is compressed, and 
somewhat resembles a Scaphite. 
57. A. selligujnous. —The Sclliguinous Ammonite, pi. X. 
fig. 3. 
Ammonites Icevigatus . Sowerby, Min. Conch. VII. p. 93, 
pi. 540, fig. I. 
Discoidal, smooth ; inner volutions few, almost wholly 
inserted, the outer one enlarging rapidly ; external margin or 
ambit obtuse; aperture very narrow, forming an elongated 
ellipsis, which is rendered sagittate by the indentation of the 
volution. 
Discovered in the Folkstone Marie, near Warminster, by 
Miss Bemu t, and found at Cheriton, near Sandgate, Kent, in 
the Tile clay, by Dr Fittom. 
58. A. cinctus,— The Girdled Ammonite, pi. X. fig. 4. 
Ammonites cinctus. Mantell, Geology of Sussex, p. 116; 
Sowerby, Min. Conch. VI. p. 122, pi. 564, fig. 1. 
Discoidal, subumbilicate ; volutions three, depressed, three- 
fourths inserted, with transverse, annular, bifurcate, undulated 
ribs ; umbilicus expanded, with a marginal zone of oblique 
tubercles ; ambit convex, embraced by the ribs ; aperture 
ovato-sagittate. 
Mantell says of his specimen, “ The volutions, although 
compressed, have a slight degree of convexity, and are orna¬ 
mented by transverse radiations that arise from a row of small 
tubercles on the inner margin. Each radius (rib) divides into 
two branches, which pass with a gentle sweep across the 
ambit, and unite with the corresponding undulations of the 
D 
