ZONE OF ARIETITES RARICOSTATUS. 



59 



Ammonites Driani, Bumort. 



— Salisburgensis, Hauer. 



— Ssemanni, Dumort. 



— Bonnardi, d'Orb. 



— Nodotianus, d'Orb. 



— Pellati, Dumort. 



— armentalis, Dumort. 



— Edmondi, Dumort. 



Ammonites Oosteri, Dumort. 



— planicosta, Sow. 



— subplanicosta, OppeJ. 



— tardecrescens, von Hauer. 



— viticola, Dumort. 



— raricostatiis, Ziet. 



— vellicatus, Dumort. 



— ziplius, Hehl. 



Gasteropoda. 



Pleurotomaria gigas, Deslong. 



Pleuromya Toucasi, Dumort. 



— cylindrica, Dumort. 

 Hippopodium ponderosum. Sow. 

 Gryphsea obliqua, GoJdf. 



Pleurotomaria Ciiarmassei, Dumort. 



COXCHIFERA. 



Myoconcha oxynoti, Querist. 

 Harpax nitidus, Dumort. 

 Waldlieimia cor, La.mk. 

 Terebratula Sinenmriensis, Opj). 



M. Duraortier includes in his zone of Ammonites oxi/notus many species already 

 enumerated in my description of the Obfusus- and Baricostafuszones ; it is well, 

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

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

 comprehend under the name of the 'zone de I' 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. 



Palaeontology. 







metres 



Couches a 



Calcareous beds, consisting of 







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



Am.raricostatus. 



light-coloured limestones ... 



1 







Cardima philea. 



Couches a. 



Subcrystalline calcareous beds, 







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



Am. oxi/notus. 



reddish, or brown-yellow 







Bonnardi, Nautilus pertextus, Avicula Sine- \ 





compact limestone 



1 



50 



murtensis. 



Couches k 



Hard sublameliated greyish 







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



Am. stellaris. 

 Couches k 



limestone 



3 







phcea obliqua, Waldheimia cor. 

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



Hard sublameliated bluish- 



Am. Davidsoni. 



grey limestone 



Total thickness 



1 



50 



Pentacrinus tuberculatus. 



7 







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

 comprehends the Raricostatus-^ Oxynotus-, and Obtusus-hed^% 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 



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



