58 



THE LIAS AMMONITES. 



on closer study that Amaltheiis Lynx, d'Orb., and Amal. Coynarii, d'Orb., from the 

 Middle Lias " du Bois-de-Trousse, pres de Saint Amand {Cher), oil elle est passe'e a 

 Vetat de fer sulfure ou de fer hydrate,'' be French forms of Amal. oxynotus. I failed to 

 find the type of AmaL Lynx and Amal. Coynarti in the d'Orbignyan Collection in the 

 Jardin des Plantes. 



Erom the Bassin du Rhone M. Duraortier has given a very full list of the fossils 

 in his collection which he refers to this zone, and observes/ when studying the fossils of 

 the zone de Y Ammonites oxytiotus, the fact that strikes one most is the important place 

 which the Ammonites occupy. The number and variety of the species^ the abundance of 

 certain types, and above all the invariable regularity of their stratigraphical position, well 

 deserve attention. In relation to their form, the Ammonites of the superior zone cannot 

 be attached by preference to any particular type, inasmuch as we recognise at the same 

 time shells with numerous and narrow whorls extremely evolute and provided relatively 

 with an enormous umbilicus, as well as species entirely convolute and without a 

 trace of umbilicus ; certain forms having large, round backs, whilst others are provided 

 with sharp and prominent carinas. The external ornamentation exhibits the same variety ; 

 sometimes the shell is simple and without ornament, whilst in others the surface is 

 provided with the richest decoration. 



The Gastropods, less rare than in the lower zone, are not, however, of much 

 importance. Among the Lamellibranchiata the Gryphaa obliqua occcupies an excep- 

 tional position by the immense number of its individuals. The Pleuromym in this 

 division of the Lias attain their maximum development ; and the Cardinia philea, d'Orb., 

 and Hippopodium ponderosum, Sow., in consideration of their remarkable forms and the 

 certainty of their horizon, ought to be especially noted. The Brachiopods are here repre- 

 sented by Spiriferina and Rhynchonella, abounding in individuals, and above all by the 

 Waldheimia cor, Lamk., a species of the highest importance. The Echinoderms are in 

 general few in number and species, but Pe?ifacrinus tuherculatus is inferior to no other fossil 

 in the zone for its importance and the number of its individuals. The following list gives 

 the characteristic fossils of the zone of Ammonites oxynotus as defined by M. Dumortier : 



Cephalopoda. 



Belemnites acutus, Mill. 

 Nautilus pertextus, Dumort. 

 Ammonites resurgens, Dumort. 

 — • Hartmanni, Oppel. 



— Berardi, Dumort. 



— Patti, Dumort. 



— lacunatus, Buck. 



— obtusus, Soiv. 



— stellaris, Sow. 



Ammonites ffiduensis, Pharmasse. 



— Landrioti, cV Orb. 



— Locardi, Dumort. 



— Birchii, Sow. 



— Sauzeanus, (TOrb. 



— Victoris, Dumort. 



— Aballoensis, iV Orb. 



— oxj'notus, Quenst. 



— altus, Hauer. 



'Etudes Paleontologiques sur les Depots Jurassiques du Bassin du Ehone,' torn, ii, p. 238, 1867. 



