354 Notices of Memoirs — E. Favre — Zone of A. acanthicus. 



nsrooTioiEs oip isvCisivnon^s. 



I. — On the Zone of Ammonites acanthicus or Ammonites 



TENUILOBATUS.^ 



IN an elaborate memoir descriptive of the fossils and localities of 

 tlie zone of Am. acanthicus in the Swiss and Savoy Alps, M. E. 

 Favre, after a careful comparison of the fossils with those from other 

 Jurassic strata, together with remarks on the nature and age of the 

 fauna of this zone, gives the following resume of his researches. 



1. There is no general break in the Upper Jurassic strata in 

 the Alpine or Mediterranean regions. 



2. The zone of Am. acanthicus of the Alps of Switzerland and of 

 Savoy is the equivalent, in the Eastern Alps, of the zone of Am. 

 tenuilobatus, and Am. isotypus and of the zone of A. Becheri. 



3. It is the equivalent, in the Jura, of the zone with Am. tenuilohatus, 

 and of the zone with Am. Eudoxus and Am. pseiidomutabilis. 



4. The zone of Am. tenuilobatus is the exact equivalent of the 

 Astarte zone (terrain astartien), of which it is only a peculiar facies. 



5. The stratigraphical position of the zone Am. acanthicus and its 

 palasontological affinities unite it closely with the Kimmeridgian. 



6. In all the Alpine region, there is a very marked palteontological 

 line between the zone of Am. acanthicus and the strata upon which 

 it reposes, which are, either the zone of Am. transversarius or of Am. 

 himammatus. The latter has more affinity with the subjacent strata 

 and ought to be classed in the Oxfordian. There is, on the con- 

 trary, a close paleeontological relation between the zone with Am. 

 acanthicus and the Tithonian strata which overlie it, 



7. The general classification which would best suit the whole of 

 the Alpine strata would be to fix the upper limit of the Oxfordian at 

 the base of the zone with Am. acanthicus, and to give the name of 

 Kimmeridgian (or Alpine Kimmeridgian) to the whole of the beds 

 comprised between the Oxfordian and the strata of Berrias or the 

 base of the Neocomian. This name should be employed here in 

 the sense which M. Waagen gave to it in I860 ; and which M. Loriol 

 also attributes to it; except a slightly less extension of the lower 

 part, the last author makes it to include all the strata to the zone of 

 Am. transversarius. However, this latter difference is not very im- 

 portant in this region, since the Corallian /ac2es inferior to the zone 

 of Am. acanthicus is not here developed. The zone with Am. 

 acanthicus would be the Lower Kimmeridgian, and the Tithonian 

 beds the Upper Kimmeridgian. The equivalents of the Jurassic 

 and Alpine facies are approximately given in the accompanying 

 Table: 



1 E. Favre, La Zone a Ammon. acanthicus dans les Alpes de la Suisse et de la 

 Savoie. — P. De Loriol, Monographic paleontologique de la Zone a Am. tenuilobaUts 

 de Baden. — Memoires de la Societe Paleontologique Suisse, Basel, lb77, vols. 3, 4. 



