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 tlie Gray Chalk Marie at Middleham, Sussex, by 

 G. Mantell, Esq. 



59. A. CATiLLUs. — The Porringer Ammonite, pi. X. fig. 5. 

 Ammonites catillus. Sovverby, 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 Petersfield, by Mrs Murchison. 



60. A. MuRCHisoN/E Murchison's Ammonite, ])!. X. fig. 6. 



Ammonites Murchisona. 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 slight!}' 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 tlie 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 Allingtoii 

 near Bridport. 



Named in honour of that scientific lady. 



61. A. spiNosus.^ — The Spined Ammonite, pi. X. figs. 7, 

 8,9. 



Ammonites spinosiis. Sovverby, 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, 

 pl. 540, fig. I. 



Discoidal, compressed ; four partly exposed volutions, flat- 

 tened on the edge, and provided witii a row of ten or twelve 

 conical obtuse tubercles on each side, all of wiiicii are 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 H.H. Goodhall, Esq. 



This species may be distinguished from the Ammonites 

 tuberczilattis, pl. XIV. fig. 1, and the A. laulus, pl. VIII. 

 fig. 1, by the blunt and depressed termination of the ribs upon 

 the back. 



63. A. BuoDicEi. — Brodie's Ammonite, pl. X. fig. 13. 

 Ammonites Brodicei. Sowerby, Min. Conch. IV. p. 71, 



pl. 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. HuMPHRiEsiANUS Humphries' Ammonite, pl. X. 



figs. 14, 15. 



Ammonites Hiunphriesianus. Sowerby, Min. Conch. V. 

 p. 161, pl. 300, 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. PERAMPLUs. — The Very Large Ammonite, pl. XI. 

 fig. 1. 



Ammonites peramplics. Mantell, Fossils of the South 

 Downs, p. 200 ; Sowerby, Min. Conch. IV. p. 79, pl. 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. 



