354 PROF. E. FORBES ON LOWER GREENSAND FOSSILS. 



151. Ammonites Martinii D'Orbigny, T. C. pi. 58. f. 7 — 10. 



Loc. Atherfield, frequent in the upper beds, and growing to a 

 considerable size. The figure (pi. v. fig. 3.) represents a young 

 specimen from that locality. Identified with French specimens. 



152. Ammonites Cornuelianus D'Orbigny, T. C. pi. 112. f. 1, 2. 

 Loc. Hythe. 



153. Ammonites Hambrovii. Sp. no v. PI. v. f. 4. 



A. testa discoidea, inflata, profunde umbilicata, transverse 

 costata, costis numerosis, crassis, rotundatis, insequalibus, 

 tuberculis magnis, latis, prominentibus, marginis interni 

 anfractuum plerumque orientibus ; dorso lato, rotundato ; 

 apertura dilatata, lata, reniformi, lateraliter uni-tuberculata ; 

 septis lateraliter bilobatis, lobis lateralibus obscuris, lobo 

 dorsali maximo, sella laterali superiori latissima. 



Diam. 2f ; crass. If ; lat. apert. 1^ unc. 



Shell ventricose, suborbicular, deeply umbilicated, the umbilicus 

 rather narrow, exposing about one-third of three inner volutions, 

 very steep at their sides. Whorls with large broad and strong 

 tubercles, variable in relative size, studding the margins of the 

 umbilicus, and each giving rise to two, or, in some cases, three 

 strong rounded ribs, which run over the back without interrup- 

 tion. A similar rib is seen between each pair of tubercles. The 

 last whorl suddenly increases in breadth. The back is very 

 slightly depressed. The mouth is broad and reniform, and is 

 angled on each side by a single tubercle. The septa of the 

 chambers are well seen on most of the specimens from Atherfield. 

 They consist of a dorsal lobe, and two or sometimes three lateral 

 lobes. The dorsal lobe is largely developed, and is composed of a 

 broad quadrate base with pinnated sides, and two long pinnated 

 terminal branches. The lateral lobes are but slightly developed 

 and very distant. The superior lateral saddle is very broad, large, 

 and rounded, and divided at its margin by crenated lobations. 

 The dorsal saddle is small and ovate. The other lateral saddles 

 are small and shallow. 



This species belongs to M. D'Orbigny's group of Anguli-costati. 

 It is frequent in the Cracker bed at Atherfield. It was sent to 

 France and returned as Ammonites Cornuelianus. It differs 

 however so materially from M. D'Orbigny's figures and description 

 of that species, and from British specimens, which exactly agree 

 with those figures and that description, that I do not hesitate to 

 regard it as distinct. It may be distinguished from A. Cornuel- 

 ianus by the following characters: 1st, peculiarity of form 

 dependent on the rapid increase of the volutions ; 2d, position of 

 the large tubercles and absence of the second series of tubercles, 

 which, together, give the aperture of A. Cornuelianus a qua- 

 drangular form ; 3d, form of the chambers, the dorsal lobe in 

 A. Cornuelianus being much broader and its branches more 



