436 THE LIAS AMMONITES. 



bifrons, and Harpoceras Levisoni ; it is distinguished from Harpoceras radians by having 

 wider and flatter whorls, a less circumscribed keel, with less prominent ribs, a lateral 

 sulcus, and a different suture-line. It is distinguished from Harpoceras bifrons 

 by having wider whorls, smaller and more numerous rugose ribs, with a much smaller 

 and shallower lateral sulcus, the want of the tricarinated and bisulcated siphonal area, 

 and a difference in the structure of the lobes and saddles. It difi'ers from Har20oceras 

 Levisoni in having wider and less involute whorls, of the same form and structure in 

 youth as in adult age ; whilst in Harp. Levisoni the young shell has large obtuse ribs, 

 and a carina with lateral sulci, and style of building resembhng the young shells of the 

 genus Arieiites. 



Locality and Etratigrapldcal Position. — liar^^oceras serpentinum has been collected 

 from the zone of Harpoceras bifrons at Stinchcombe, Erocester, and Stroud, in Gloucester- 

 shire ; Bloxam, Oxfordshire ; and many localities in Rutland ; from the Santon Railway- 

 cutting, in north-west Lincolnshire ; and from numerous exposures of the Upper Lias on 

 the Yorkshire coast, and known there under the names A. Mulgraviiis saAfalcifer. 



Foreign Correlations. — I have devoted several pages of this work to the correlations 

 of the Upper-Lias beds of north and south Germany, and several of the departments of 

 France, and I must refer to pages 129 — 136 for ample details on the correlation of the 

 Harp.-serpentinum beds in these countries. 



Harpoceras bifrons, Brugidere, 1793. PI. LIX, figs. 1 — 4. 



CoKNU Ammonis, Lister. Hist. Animal. Anglise, tab. vi, fig. 2, 1678. 



— — Baier. Oryctogr. noric, p. 65, tab. iii, fig. 9, 1708. 



— — Rumphius. Thesaurus, tab. &0, fig. A.D., 1739. 



— — Lister. Synop. Conch. (Edit, alt.) tab. 1041, fig. 20, 17/0. 



— — Waleott. Petrifactions near Bath, p. 32, fig. 41, 1775. 

 Ammonites bifeons, Bmguibre. Encycl. Method., torn, i, p. 40, 1792. 



— — Bosc. Bufibn de Deterville, torn., v, p. 176, 1801. 



— — ScJilotheim. Taschenbuch, p. 35, 1813. 



— Waicotti, Sowerhy. Mineral Conchology, vol. ii, p. 7, pi. 106, 1815. 



— HiLDENSis, Young and Bird. Geol. Yorksh. Coast, pi. xii, fig. 1, 1822. 



— BIFRONS, Haan. Amm. et Goniat.,p. 108, No. 13, 1825. 



— — Beshayes. Coquilles character., p. 236, pi. 7, fig. 7, 183 1. ' 



— — Giebel. Fauna der Vorwelt, Bd. iii, p. 518, 1852, 



— — d'Orhigny. Paleont. Frangaise, Terr. Jurass., p. 219, pi. 56 



1842. 



— — Quenstedt. Cephalopoden, p. 108, t. 7, figs. 13, 14, 1849. 



— — Chapuis et Dewalque. Terr, second. Luxemb., p. 66, pi. ix, 



fig. 3, 1854. 



— Walcotti, Simpson. Foss. Yorksh. Lias, p. 99, 1855. 



