ZONE OF ARIETITES RARICOSTATUS. 



59 



Ammonites Driani, Dumort. 



— Salisburgensis, Hauer. 



— Ssemanni, Dumort. 



— Bonnardi, d'Orb. 



■ — Nodotianus, d'Orb, 



— Pellati, Dumort. 



— arraentalis, Dumort. 



— Edmondi, Dumort. 



Ammonites Oosteri, Dumort. 



— planicosta, Sow. 



— subplanicosta, Oppel. 



— tardecrescens, von Hauer. 



— viticola, Dumort. 



— raricostatus, Ziet. 



— vellicatus, Dumort. 

 ■ — • ziplius, Hehl. 



Gasteropoda. 



Pleurotoraaria gigas, Deslong. 



Pleuromya Toucasi, Dumort. 



— cylindrica, Dumort. 

 Hippopodium ponderosum, Sow. 

 Gryphaea obliqua, Gold/. 



Pleurotomaria Charmassei, Dumort. 



CoNCHIFERA. 



MyocoDcha oxynoti, Quenst. 

 Harpax nitidus, Dumort. 

 Waldheimia cor, Lamk. 

 Terebratula Sinemuriensis, 0pp. 



M. Dumortier includes in bis zone of Ammonites oxynotm many species already 

 enumerated in my description of the Obtusus- and Baricostatus-iones ; it is well, 

 therefore, to understand this author's definition of the group he has so well described 

 and so fully illustrated. He says, " the superior part of the Lower Lias, which I 

 comprehend under the name of the 'zone de l' Ammonites oxynotus^ offers an ensemble 

 of beds of a total inconsiderable thickness, but which may be represented by the 

 following theoretical section, taking the beds in descending order from above downwards."^ 



Zones. 



Petrology. 



Thick- 

 ness. 



PaljEOntology. 



Couches a 

 Am.raricostatui. 



Couches a 

 Am. oxynotus. 



Couches k 

 Am. stellaris. 



Couches k 

 Am. Davidsoni. 



Calcareous beds, consisting of 

 light-coloured limestones ... 



Subcrystalline calcareous beds, 

 reddish, or brown-yellow 



metres 

 I 



1 50 

 3 

 1 50 



Am. raricostatus, A. planicosta, A. viticola, 

 Cardinia philea. 



Am. oxynotus, A. Aballoensis, A. Driani, A. 

 Bonnardi, Nautilus pertextus, Avicula Sine- 

 muriensis. 



Am. stellaris, A. (Eduensis, A. obtusus, Gry- 

 phaa obliqua, Waldheimia cor. 



Am. Davidsoni, A. lacunatus, A. Hartmanni, 

 Pentacrinus tuberculatus. 



Hard sublamelkted greyish 

 limestone 



Hard sublamellated bluish- 

 grey limestone 



Total thickness 



7 



It is evident from the above table that Dumortier's " zone de l' Ammonites oxynotus " 

 comprehends the Raricostatus-, Oxynotus-, and Obtusus-hedi?, of this Monograph. 



The distribution of the Ammonites in this zone has been very carefully observed and 

 noted by this author, and he has therefore called the special attention of palaeontologists 

 ^ ' Etudes Paleontologiques sur les Depots Jurassiques du Bassin du Rhone,' torn, ii, p. 95, 1867. 



