27 
[ Hyatt t 
common to all of the higher beds of the Lower Lias, but also some 
species which occur only in the Middle and Upper Lias of the ba- 
sins farther to the west. 
So far as we have seen the forms, or noted the observations of 
others on the species of the Adnether and Hierlatz basins in the 
Northeastern Alps, this last extreme opinion does not seem to be 
sustained. That the faunas are mixed, as noted above, seems to be 
established, however, by the direct observations of several authors, 
notably Geyer and Herbich. 
These facts appear also to accord perfectly with the conclusions 
given above. If the Northeastern Alps were the seat of origin for 
the radical series during the time of deposition of the earlier beds, 
and the more western basins became the originating centres of the 
more progressive series, and, finally of the degradational series dur- 
ing Bucklandian and later times, then we can account for this con- 
fusion as due to return migrations from the western faunas towards 
the east. The radicals of the different progressive series could then 
have arrived in the Northeastern Alps with sufficient rapidity of 
succession to have become mixed in the same rocky stratum ; and 
the later forms may even have overtaken the radicals while on their 
journey to the east and have arrived together in this basin, which 
would thus have become changed from an autochthonous to a re- 
sidual fauna. 
Another fact in favor of this view is the curious confirmation af- 
forded by Neumayer’s remarkable conclusion that the faunas of 
the Mediterranean province are distinguished by the earlier ap- 
pearance and origin in them of the Lytoceratidae, a family which 
is characteristic of the Middle and Upper Lias in Central Europe. 
This opinion is well sustained by the later observations of Geyer 
at Hierlatz, and especially by Herbich’s discovery of an extensive 
series of these forms in the Lower Lias of Siebenburgen. 
The rise of the Arietidae is, in large part, more completely re- 
corded in the Northeastern Alps, than in any other basin, but the 
acme of its history was reached in the faunas of South Germany, and 
the Cote D’Or. The records of its declining series are about equally 
well given in the rocks of the Lower Lias in South Germany and 
Cote D’Or ; and in England there is also a very complete series, 
especially of what may be called the more degraded forms of As- 
teroceras, and of the first or oxynotum sub-series of Oxynoticeras. 
The faunas of the Italian peninsula have not been completely ex- 
