Ammonites. 



MOLLUSCA. 



25 



inserted 

 as they 

 a deep 



the dorsal furrow ; the carina but slightly raised, with a 

 furrow on botli 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, fiu'. 1 and 2. Fleming, Brit. An. p. 245. 



Discoidal, thick, subumbilioate ; 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 verj' 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. cRENULARis.— The Crenulated Ammonite, pi. 

 XVII 1. fig. 8. 



Ammonites crenularis. Phillips, Geology of Yorkshire, I. 

 p. 164, pi. 12, fig. 22. De la Beche, Geo. Manuel, p. .372. 



Lenticular, umbilicate ; with five two-thirds 

 volutions, the inner ones decreasing in thinness 

 approach towards the central one, and forming 

 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 pass over the back, and returning rapidly 

 and continuouslj' 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. Sowerb}', 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. Braikenridgii. — Braikenridge'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 sliort distance from the last 

 rilj, suddenly expands on tlie 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 Dundrj', near Bristol, 

 by G. W. Braikenridge, Esq. and named in honour of him. 



145. A. Ci EVLANDiciJS. — The Clevland Ammonite, pi. 



xvin. fig. 11. 



Ammonites Clevlaiidicus. — Phillips, Geology of Yorkshire, 

 L 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, thickt ned 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 Staillies, Yorkshire, in the Lias. 



146. A. HETEUOGENus. — The Heterogenus Ammonite, 



pi. xvin. fig. 12. 



Ammonites heterogenus. Phillips, Geology of Yorkshire, 

 L p. 163, pi. 12, fig. ly. De la Beche, Geo. Manuel, p. 371. 



Discoidal, somewhat comjiressed ; 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 ertigatus. 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 Lias Shale of Yorkshire. 



148. A. FUNATUS. — The Ropey Ammonite, pi. XVIII. 

 fig. 14. 



Ellipsolithes funatus. Sowerby, Min. Conch. I. p. 81, pi. 

 32. Natilus funatus. 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 



