14 
MOLLUSCA. 
Ammonites. 
opposite side ; small oblique tubercles are placed on each 
radius at the point of bifurcation.” The ambit is slightly 
undulated by the ribs. Greatest diameter three inches and 
six-eighths; thickness of the outer volution one inch and a 
half; of the aperture one and an eighth of an inch. 
This species somewhat approaches in appearance to Am¬ 
monites varians , in having bifurcated ribs, and a row of 
tubercles on the inner margin, but is widely different by the 
rounded form of its back, and other obvious distinctions. 
Found in the Gray Chalk Marie at Middleham, Sussex, by 
G. Mantell, Esq. 
59. A. catillus. —The Porringer Ammonite, pi. X. fig. 5. 
Ammonites catillus . Sowerby, Min. Conch. VI. p. 123, 
pi. 564, fig. 2. 
Discoidal, much compressed ; three or four volutions, two- 
thirds concealed, their inner margins narrow and obtuse; 
sides even, with a row of short tubercles on each side of the 
margin, which are transposed into obscure undulations on the 
outer volution; aperture lanceolate-sagittate, with obtuse 
angles. Greatest diameter six inches ; thickness not quite 
an inch. 
Discovered in the upper Green-sand in a quarry at Nursted, 
near Peters field, by Mrs Murchison. 
60. A. Murchison a;. —Murchison’s Ammonite, pi. X. fig. 6. 
Ammonites Murchisoncv. Sowerby, Min. Conch. VI. p. 95, 
pi. 550. 
Discoidal, carinated ; six or seven compressed volutions, 
with obtusely truncated inner edges, producing a concave 
surface, the inner ones about two-thirds concealed ; sides 
provided with obtuse undulations or lines of growth, which 
are usually bifurcate as they approach towards the rounded 
ambit; aperture semi-elliptical, its sides are slightly produced 
lobes ; keel but slightly protruding, and containing the 
siphuncle. 
In the young condition the sides of this Ammonite are 
furnished with transverse ribs, which are irregular in their 
development, and exist until the fossil is about two inches in 
diameter, when they become suddenly smooth, exhibiting only 
lines of growth. 
Discovered by Mrs Murchison in a calcareous nodule, at 
the base of a micaceous Sandstone rock, east of Holme, near 
Portree, Isle of Skye, and in the inferior Oolite at Allington 
near Brklport. 
Named in honour of that scientific lady. 
61. A. spinosus. —The Spined Ammonite, pi. X. figs. 7, 
8, 9. 
Ammonites spinosus . Sowerby, Min. Conch. VI. p. 78, 
pi. 540, fig. 2. 
Discoidal; four volutions, inner ones exposed ; with nume¬ 
rous sharp, forked ribs, which become nearly lost as they pass 
towards the ambit; aperture subrotund. 
When young, the ribs of this shell are furnished with four 
rows of spines, about twenty on each, which are connected at 
their base by two or three ribs on each ; these gradually dis¬ 
appear by age; when the shell has reached an inch in diameter, 
they are almost entirely extinct, leaving only sharp, irregular 
ribs. 
Found in Clay near Weymouth, and also at Braunston. 
62. A. denarius. —The Denier Ammonite, pi. X. figs. 
10, 11. 
Ammonites denarius . Sowerby, Min. Conch. VI. p. 78, 
pi. 540, fig. 1. 
Discoidal, compressed ; four partly exposed volutions, fiat- 
toned on the edge, and provided with a row of ten or twelve 
conical obtuse tubercles on each side, all of which arc united 
to two ribs, with usually a third rib between each, and there 
are in all about thirty arcuated ribs, which terminate abruptly 
near the back, but none of these extend beyond the tubercles 
on the interior sides of the volutions; aperture oblong, which 
in the young state is longer than wide, with the tubercles but 
slightly elevated. 
Discovered on Blackdown Common by II.H. Goodhall, Esq. 
This species may be distinguished from the Ammonites 
tuberculatus, pi. XIV. fig. 1, and the A. lautus , pi. VIII. 
fig. 1, by the blunt and depressed termination of the ribs upon 
the back. 
63. A. Brodkei. —Brodie’s Ammonite, pi. X. fig. 13. 
Ammonites Brodicei. Sowerby, Min. Conch. IV. p. 71, 
pi. 351. 
Discoidal, gibbous, very largely umbilicate ; seven nearly 
half concealed volutions, provided with distant transverse 
strong ribs, the intervening sulci being about equal in breadth ; 
these emanate from near the edges of the volutions, and 
extend to the centre, where they become very broad, and are 
each ornamented by an obtuse, nearly round tubercle, from 
whence proceed numerous lesser, slightly curved ribs, which 
pass over the rounded ambit, to the number of about four to 
each of the larger ribs, and meet the strong tubercular ribs 
on the opposite side; aperture curved and transversely oblong; 
greatest diameter nearly four and a half inches. 
Found on Portland Island by James Brodie, Esq. 
64. A. Ilt/MPHRiEsiANUS.—Humphries’ Ammonite, pi. X. 
figs. 14, 15. 
Ammonites Ilumphriesianus. Sowerby, Min. Conch. V. 
p. 161, pi. 500, fig. 1. 
Discoidal, very thick ; with five volutions, the inner ones 
exposed; sides ornamented with large, numerous, distant 
ribs, extending to nearly the centre of the volutions, where 
they are provided with large oblong-ovate, somewhat conical 
tubercles, from whence they branch into three arcuated 
smaller ribs, and passing over the greatly rounded ambit, 
meet at the tubercles on the opposite side ; in the inner 
volutions the tubercles are placed close to the suture, or line 
of separation; these inner volutions are much flatter on the 
back than the others, consequently producing quadrangular 
sections; aperture in the young shell arcuated, oblong, and 
in the older shell semilunar. 
Found in the inferior Oolite of Sherborne. 
65. A. per amplus. —The Very Large Ammonite, pi. XI. 
%• !• 
Ammonites peramplus. Mantell, Fossils of the South 
Downs, p. 200 ; Sowerby, Min. Conch. IV. p. 79, pi. 357- 
Discoidal, four or five ventricose volutions, the inner ones 
nearly half inserted, the outer one increasing rapidly in 
dimensions, and occupying one-third the diameter of the 
disk ; sides provided with a few, distant, obtuse ribs, which 
are most conspicuous on the inner sides of the volutions, and 
become obsolete before reaching the rounded and plain *. 
ambit; aperture transversely obovate ; septa crisped and 
deeply sinuated. 
Discovered by G. Mantell, Esq. near Lewes. From the 
great dimensions of some fragments found by that gentleman, 
he supposes the diameter of the shell must have been about 
three feet in its perfect condition. 
