Ammonites. 
MOLLUSCA. 
19 
appearance of Ammonites biplicatus , figs. 8. of this plate, but 
differs from it in the situation and size of its tubercles, and 
in their being united by single ribs, which are not curved ; 
in the volutions being less inserted; in the ambit being 
sulcated ; and in the marginal tubercles being opposed to each 
other in place of alternating, which character also separates it 
from A. auritus , pi. VII. fig. 9. 
97. A. Stokksii—S toke’s Ammonite, pi. XIV. fig. 2. 
Ammonites Stohesii. Sowerby, Min. Conch. II. p. 205, pi. 
191; De la Beche, Geo. Manuel, p. 374; Fleming, Brit. 
An. p. 242. 
Lenticular, depressed ; inner edge of volutions strongly 
defined ; crossed by numerous slightly elevated ribs, which 
are narrow at their interior side, and gradually thicken as 
they approach the ambit, where they have a slight curvature 
towards the aperture, and become obsolete near the back of 
the shell ; inner volutions half concealed ; ambit thin and 
crenulated ; the whole shell exhibits marks of concentric striaa; 
aperture sagittate. 
Found by Professor Buckland in a Marl bed, in the inferior 
Oolite series, near Bridport, Dorsetshire, and named in honour 
of Charles Stokes, Esq. a zealous and accomplished naturalist. 
It also occurs in the middle of England. 
98. A. proboscideus. —The Proboscis Ammonite, pi. XIV. 
fig. 3. 
Ammonites jwoboscideus. Sowerby, Min. Conch. IV. p. 
4. pi. 310, fig. 4, 5 ; Fleming, Brit. An. p. 246. 
Depressed, with four or five ventricose partly concealed 
volutions ; outer one provided with two rows of large, remote, 
blunted, almost cylindrical tubercles ; the inner series con¬ 
tinuing along the exposed portion of the central volutions, 
and marking their line of separation ; ambit concave, with 
the outer series of large tubercles on both its edges ; aperture 
orbicular, its width being about a third of the diameter of the 
shell. 
Sowerby mentions two varieties of this species. 
1. With the tubercles connected by very irregular and 
short ribs. 
2. Destitute of ribs. 
This species is distinguished from the A. tuberculatus , fig. 
1. of this plate, by having only eight tubercles on each volu¬ 
tion, in place of twelve, which marks that species; it has also 
a broader and ill defined back, with a very large siphuncle. 
Found in the Marl, under the Chalk at Folkstone, Cam¬ 
bridge, and other places. 
99. A. dentatus. — The Toothed Ammonite, pi. XIV. 
fig. 4. 
Ammonites denlcitus. Sowerby, Min. Conch. IV. p. 3. pi. 
308; Fleming, Brit. An. p. 244. A. serratus; Parkinson, 
Geolo. Trans. V. p. 57. 
Discoidal, umbilicated ; with numerous, prominent, slightly 
curved ribs, furcated near their origin, and terminating upon 
the margin of the ambit, where they are a little thickened 
and bent forward ; producing on each side of the back a 
serrated margin, with a plain, fiat, intermediate space; aper¬ 
ture, two-fifths of the diameter of the shell, long, and one- 
fourth wide. 
Found in the Marie below the Chalk at Folkstone. 
100. A. Hystrix. — The Hedgehog Ammonite, pi. XIV. 
fig. 5. 
Ammonites Hystrix . Phillips, Geology of Yorkshire, I. p. 
123, pi. 2, fig. 44 ; De la Beche, Geo. Manuel, p. 294. 
Discoidal, volutions moderately inflated, furnished with 
transverse elevated ribs, emanating from the inner margin,— 
which is well defined, and terminating on the ambit, where 
they have a gentle curve forward ; each rib provided with 
three series of tubercles, all of which appear to have been 
elevated, subulate, and sharp pointed ; those on the inner 
margin, a quarter of an inch in length, and pointing back¬ 
wards ; the central series are obtuse, as if worn down ; while 
the dorsal ones, which are entire, are nearly half an inch in 
length, and are curved forward. 
Found in the Speeton Clay at Speeton, Yorkshire. 
Professor Phillips says, this species is “allied to Ammonites 
Mantelli , of which it may prove to be one of the many 
varieties which, in Sussex, lie in the gray Marie.” We, how¬ 
ever, cannot agree with the professor in this opinion. 
101. A. Woolgari —Woolgar’s Ammonite, pi. XIV. fig. 
6, 7. 
Ammonites Woolgari. Man tell, Geology of Sussex, p. 197, 
pi. 21, fig. 16, and pi. 22, fig. 7 ; Fleming, Brit. An. p. 242 ; 
De la Beche, Geo* Man. p. 372 and 383 ; Sowerby, Min. 
Conch. VI. p. 165, pi. 587, fig* 1* 
Discoidal, depressed, carinated ; with three or four volu¬ 
tions, the central ones one-third inserted ; sides of the 
central volutions compressed, and ornamented with remote, 
slightly curved ribs, inclining towards the aperture, termina¬ 
ting on the outer margin in compressed, carinated tubercles, 
or spinous projections ; keel acute and deeply serrated. In 
some specimens, there are two tubercles on the outer extre¬ 
mity of each rib, and one on the inner margin. 
Found in the Lower Chalk, near Lewes, Sussex. 
So different ar e the central volutions of this fossil from the 
external one, that they might easily be mistaken as belonging 
to distinct species, if separated from each other. They are 
considerably compressed, and provided with elevated, curved 
ribs ; while the outer one is inflated, and provided with ten 
large, conical, spinous, parallel tubercles, on each side of the 
keel, one tooth of which is in the centre of each pair. In the 
central volutions, every rib is furnished with a depressed 
tubercle, placed near to, and parallel with, the carina. Within 
this is placed a smaller tubercle, which increases considerably 
in size with the volutions as they progress, and becomes 
united with a third tuberculous eminence, which gradually 
diverges from the inner edge of the volution, until it becomes 
obsolete ; the depressed tubercles being still, however, visible. 
This species was named by Mr Mantell in honour of the 
late Thomas Woolgar, Esq. a zealous and acute topographer 
and naturalist. 
102. A. bi 1 ’Li cat us. — The Two Plaited Ammonite, pi. 
XIV. fig. 8. 
Ammonites biplicatus. Mantell, Geology of Sussex, p. 9L 
pi. 22, fig. 6 ; Fleming, Brit. An. p. 248. 
Compressed, carinated, and slightly umbilicate; with three 
or four volutions, the central ones two-thirds concealed; 
crossed by transverse, prominent, curved, bifurcated ribs, 
which emanate from a series of oblong, tubercular promi¬ 
nences, situate on the inner margin of the volutions, and 
terminating in distinct tubercles on the outer margin ; keel 
depressed, bordered by alternating and compressed tubercles; 
aperture obtusely sagittate, its length being somewhat less 
than the diameter of the shell. 
Found in the Blue Chalk Marie. 
This species has some affinity to the Ammonites lautus y 
