Ammonites. 
MOLLUSCA. 
25 
the dorsal furrow; the carina but slightly raised, with a 
furrow on both sides ; aperture oblong, its length being more 
than a fourth the diameter of the last volution. Greatest 
diameter fourteen inches; thickness from three to four inches. 
Found in the Lias near Bath. 
141. A. monile. —The Necklace Ammonite, pi. XVIII. 
fig. 7. 
Ammonites monile . Sowerby, Min. Conch. II. p. 35, pi. 
117, fig. I and 2. Fleming, Brit. An. p. 245. 
Discoidal, thick, subumbilicate ; with four wholly exposed 
volutions; crossed by numerous, curved, tubercular ribs ; the 
tubercles hollow, deep in the interior, and externally obsolete 
in the margin ; these become gradually more produced and 
somewhat elongated as they approach the ambit, where the 
last one is cleft; the whole surface crossed by very fine 
divergent striae; ambit somewhat concave, with close, trans¬ 
verse striae ; aperture transversely ovate, about a third the 
diameter of the shell in length, and almost twice as wide. 
Discovered at Sandgate, near Folkstone, Kent. 
The surface of this species is frequently highly irri- 
descent. 
142. A. cjrenularis. —The Crenulated Ammonite, pi. 
XVIII. fig. 8. 
Ammonites crennlaris. Phillips, Geology of Yorkshire, I. 
p. 164, pi. 12, fig. 22. De la Beche, Geo. Manuel, p. 372. 
Lenticular, umbilicate; with five two-thirds inserted 
volutions, the inner ones decreasing in thinness as they 
approach towards the central one, and forming a deep 
umbilicus; external volution thick in the centre, rounded 
and somewhat slanting towards the inner side, and on its 
outer side, obliquing to a thin sharp ambit; the sides with 
a series of strong, elevated, somewhat remote ribs, which, 
after reaching the centre, are met by numerous smaller 
oblique ones, which passover the back, and returning rapidly 
and continuously on the opposite side produce a sharply 
crenulated ambit; aperture nearly cordiform, its length being 
almost equal to half the diameter of the disk ; width about 
half its length. 
Discovered in the upper Shale of the Yorkshire Lias 
formation. 
143. A. inflatus. —The Inflated Ammonite, pi. XVIII. 
fig. 9. 
Ammonites injlatus. Sowerby, Min. Conch. II. p. 170, 
pi. 178. Fleming, Brit. An. p. 245. De la Beche, Geo. 
Manuel, p. 294. 
Depressed, carinated; inner volutions wholly exposed, the 
external one increasing rapidly in dimensions and inflated 
towards the aperture ; sides somewhat flattened, crossed by 
large, elevated, and strong ribs, each commencing with a 
large compressed tubercle on its inner end, and furcated 
towards the ambit, the branches, in some instances, being 
divided from each other, all of them ending in elongated 
compressed tubercles on the margin of the flattened ambit; 
carina distinct, entire, and obtuse ; aperture somewhat 
quadrangular. 
Discovered in the Greensand, Isle of Wight, by Dr Buck- 
land. 
144. A. Braikenuidgii.—B raikenridge's Ammonite, pi. 
XVIII. fig. 10. 
Ammonites Braikenridgii . Sowerby, Min. Conch. II. p. 
187, pi. 184. Fleming, Brit An. p. 242. De la Beche, 
Geo. Manuel, p. 373. 
Discoidal, compressed; three or four volutions, the inner ones 
exposed, the outer one somewhat less than a third the diameter 
of the disk in breadth ; crossed by numerous, narrow, acute 
ribs, which emanate from the internal margin of the volutions, 
and almost immediately become furcate; at the base of each 
furcation, the ribs are furnished with a small blunted tubercle ; 
aperture orbicular; lip expanded into two oblong lobes. 
The lip is a remarkable feature in this shell, its base is 
square, and after continuing a short distance from the last 
rib, suddenly expands on the sides into two oblong lobes, 
which exhibit clearly the lines of growth ; its edges are acute, 
and a little inflected. 
Discovered in the Inferior Oolite, at Dundry, near Bristol, 
by G. W. Braikenridge, Esq. and named in honour of him. 
145. A. Clevlandicus.—T he Clevlaud Ammonite, pi. 
XVIII. fig. 11. 
Ammonites Clevlandicus .—Phillips, Geology of Yorkshire, 
I. p. 164, pi. 14, fig. 6. De la Beche, Geo. Manuel, p. 372. 
Discoidal ; with five volutions, the inner ones nearly half 
inserted ; from the interior margin a series of straight sharp 
ribs emanate, these terminate about the centre of the volu¬ 
tion, in an oblong, somewhat blunted tubercle ; towards the 
aperture, the ribs are longer, thickened externally, and take 
a gentle sweep towards the aperture ; the whole are met by 
numerous smaller nearly obsolete ribs, which pass over the 
thin ambit, producing a crenulated subcarinated centre; 
aperture nearly cordiform. 
Found at Staithes, Yorkshire, in the Lias. 
146. A. iieterogenus.—T he Ileterogenus Ammonite, 
pi. XVIII. fig. 12. 
Ammonites heterogenus. Phillips, Geology of Yorkshire, 
I. p. 163, pi. 12, fig. 19* Dc la Beche, Geo. Manuel, p. 37 L 
Discoidal, somewhat compressed ; volutions few, the outer 
one crossed by fourteen thick, depressed, rounded ribs, which 
pass over the back, and produce a scolloped ambit; these 
ribs occupy about five-sixths of the internal portion of the 
volutions, and are met by narrow straight ribs, which rise on 
the inner margin, and terminate after extending three- 
fourths across the shell ; these are continued to the 
aperture. 
Found in the upper Lias Shale of Yorkshire. 
147. A. erugatus. —The Wrinkled Ammonite, pi. XVIII. 
fig. 13. 
Ammonites erugatus. Phillips, Geology of Yorkshire, I. p. 
163, pi. 13, fig. 13. De la Beche, Geo. Manuel, p. 372. 
Discoidal; thick, with five volutions almost entirely ex¬ 
posed; crossed by obsolete ribs; ambit rounded; aperture 
oblong-ovate, slightly indented by the preceding volution, 
its length about a third the diameter of the disk. 
Found in the upper Idas Shale of Yorkshire. 
148. A. funatus. —The Ropey Ammonite, pi. XVIII. 
fig. 14. 
Ellipsolithes funatus. Sowerby, Min. Conch. I. p. 81. pi. 
32. Natilusfunatus. Fleming, Brit. An. p. 231. 
Elliptical ; with three or four half concealed volutions, 
crossed by numerous, simple, round, rope-like ribs, separated 
by somewhat wide grooves, and having constrictions at 
intervals, which are marked by small projections on the 
ribs ; aperture semilunar. Greatest diameter three inches ; 
thickness one and a half inch. 
Discovered in the Black Rock series, south east of Cork, 
Ireland, by Samuel Wight, Esq. 
G 
