Ammonites. 
MOLLUSCA. 
17 
volutions, with numerous, somewhat obtuse, slightly curved 
ribs, emanating from the suture, and passing over the back, 
where they become more elevated, and each rib is furnished 
with two small short spines on both sides, situate near the 
inner and outer edges of the volutions ; aperture obovate. 
Discovered in the Lias at Pabba, Western Islands of Scot¬ 
land, by R. J. Murchison, Esq.; and also in the Lias of 
Yorkshire. 
82. A. planorbis. — The Planorbis-shaped Ammonite, 
pi. XII. fig. 7- Fleming, Brit. An. p. 248. 
Ammonites planorbis. Sowerby, Min. Conch. V. p. 69. pi. 
448. Fleming, Brit. An. p. 248. 
Discoidal, with three or four smooth, rapidly increasing 
volutions, two-thirds exposed, much compressed, and crossed 
by numerous very fine lines of growth. 
This Ammonite, for the most part, exhibits, on its external 
surface, the most beautiful iridescent reflections. 
Found in the slaty clay, connected with the Lias, at Wat- 
chet, Somersetshire, and also in Lincolnshire. It is by no 
means scarce. 
83. A. Guliei.mii.—W illiams’s Ammonite, pi. XII.fig. 8. 
Fleming, Brit. An. p. 246. 
Ammonites Gulielmii. Sowerby, Min. Conch. IV. p. 5. 
pi. 311. 
Lenticular, much compressed, with a narrow and flat ambit; 
five or six exposed volutions, crossed by numerous dissimilar, 
arcuated, acute ribs ; each of the longer ones provided with a 
tubercle at their inner ends, and another at about a third of 
their length. Here they divide and alternate with shorter 
and more numerous ribs, which terminate in a border of 
round, prominent, distinct tubercles, on each side of the 
ambit ; aperture elliptical, somewhat more than one-third as 
wide as long. 
Found in the Oxford clay, south-west of England. 
It is named to commemorate Dr George Williams, Professor 
of Botany, Oxford. 
84. A. Blagdeni -Blagden’s Ammonite, pi. XII. fig. 9- 
Fleming, Brit. An. p. 245. 
Ammonites Blagdeni. Sowerby, Min. Conch. II. p. 231. 
pi. 201. Phillip’s Geology of Yorkshire, I. p. 151.; De la 
Beche, Geo. Manuel, p. 37 L 
Sub-cylindrical, very deeply umbilicate, occupying the 
entire disk; five or six volutions, almost wholly exposed, 
crossed by numerous strong radiating ribs, which gradually 
thicken as they diverge from the centre, each terminating 
upon the outer edge, by a large spiniform tubercle. The 
inner volutions arc deeply sunk, and not above an eighth of 
the thickness of the ambit, which is very broad, slightly con¬ 
vex, and fluted, to the extent of four or five furrows to each 
of the marginal tubercles ; aperture transverse, quadrangular, 
and three times as wide as long; greatest diameter, about six 
inches and three quarters ; thickness, four and a half inches. 
Found in the Great or Bath Oolite of Yorkshire, and in 
the Inferior Oolite at Diindry and also in Normandy. 
Named in memory of Sir Thomas Blagden. 
85. A. Leach 11 .—Leach’s Ammonite, pi. XII. fig. 10. 
Ammonites Leachii. Sowerby, Min. Conch. III. p. 73, pi. 
242, fig. 4. Fleming, Brit. An. p. 243. 
Compressed, with four volutions ; the inner ones half 
inserted ; crossed by numerous, undulating, pretty prominent, 
frequently furcated ribs, which are arcuated as they pass 
over the front, inclining to the aperture ; ambit sharp, 
crenated; aperture ovate. 
Found in the Lias at Weymouth ; and named in honour of 
Dr William Elford Leach, the late distinguished zoologist 
of the British Museum. 
This species is nearly allied to Ammonites Lamberti , pi. 
V. fig. I ; but differs from it in being more gibbous, and in 
the ribs being more prominent and less numerous. 
86. A. corrugatus.— The Wrinkled Ammonite, pi. 12, 
fig. 11. Fleming, Brit. An. p. 244. 
Ammonites corrugatus . Sowerby, Min. Conch. V. p. 74, 
pi. 451. fig. 3; De la Beche, Geo. Manual, p. 375. 
Discoidal, carinated ; having four volutions, crossed by 
numerous, elevated, slightly curved, and furcated ribs, the 
furcations near the centre ; the minor ones three-fourths con¬ 
cealed ; with a broad umbilicus, which exposes part of the 
inner volutions; back obtuse, with a distinct carina in its 
centre; aperture obovate. 
Found at Dundry, in the Iron-shot Oolite. 
This shell somewhat resembles the Ammonites heviuscuhts , 
pi. XVII. fig. 7> but is considerably thicker, the back broader, 
and the ribs more prominent. 
87» A. funiferus.— The Corded Ammonite, pi. XIII. 
fig. 1. 
Ammonites funiferus. Phillips, Geology of Yorkshire, I. 
p. 142, pi. 6. fig. 23. 
Lenticular, deeply umbilicate, carinated, thick in the 
centre, and thin at the external margins ; slightly and 
obscurely ribbed transversely, with stronger grooves passing 
over the thinly carinated back ; inner volutions concealed ; 
aperture acutely sagittate, much compressed, and nearly 
equal in length to half the diameter of the shell ; greatest 
diameter about four inches. 
Found in the Kelloways Rock at Scarborough. 
This species is nearly allied to Ammonites excavatus , pi. 
VI. fig. 7. 
88. A. ptychomph alus. —The Plaited-umbilicus Ammo¬ 
nite, pi. XIII. figs. 2 and 11. 
Ammonites plicomphalus. Sowerby, Min. Conch. IV. 
p. 82 and 145, pi. 359 and 404. Fleming, Brit. An. p. 244. 
De la Beche, Geo. Man. p. 370. 
Discoidal, largely umbilicate, around which are from eight 
to ten divergent, wide, somewhat acute protuberances ; 
ambit rounded and plain ; aperture ovate, about three- 
sevenths of the last volution in size ; a little straitened 
towards the back; greatest diameter about five inches and a half. 
Figure 2 represents the adult fossil, and figure 11 the 
young, in which condition it is very different from the old 
state, being provided with numerous, close, slightly bent, 
transverse furrows. 
Found in the sandstone at Bolingbroke, Lincolnshire, by 
Mr Weir ; the Kimmeridge clay, Yorkshire ; and in the 
Oxford clay, Normandy. 
89. A. lenticular is. — The Lens-shaped Ammonite, pi. 
XIII. fig. 3. 
Ammonites lenticular is, Phillips, Geology of Yorkshire, I. 
p. 142, pi. 6, fig. 25. 
Lenticular, smooth, inner volutions concealed, umbilicate, 
with a plain, slightly rounded keel ; aperture sagittate, 
equal to nearly the half of the diameter of the shell; consi¬ 
derably thickened in the centre, and sloping off towards the 
thin smoothly carinated ambit. 
Found by Professor Phillips, in the Kelloways Rock at 
Scarborough. 
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