COREELATION OF THE LOWEE TEIAS. 
Now the most important moment in the geological history of Idaho 
during the Lower Triassic epoch, the opening of a new connection be- 
tween the American and Mediterranean regions at the beginning of the 
Tirolites stage, has left only faint traces in the deposits of the Hima- 
layan Lower Trias. That this invasion of Mediterranean types did 
not take place through India, is evident from the fact that the 
admixture of such types in the Hedenstrocmia beds is extremely 
scanty, and that no fauna comparable with that of the Tirolites beds 
of Idaho has ever been met with either in the Salt Range or in the 
Himalayas. 
The difficulty of correlating the subdivisions of the American and 
Indian Lower Trias is chiefly due to the fact that the faunistic influence 
of India on the American regioji was never counterbalanced by 
an incursion of American forms into the Indian province. The 
American Meekoceras-fauna is probably— and in this opinion I agree 
entirely with J. P. Smith — of Asiatic origin, for there is nothing known 
in the American Permian that could have given rise to the forms of 
the Meekoceras zone. In India, however, no autochthonous types of 
the American Lower Trias are known, which, like Columbites, have 
reached the Mediterranean region as sporadic immigrants, but not the 
Indian Triassic province. 
Near affinities are therefore restricted to the fauna of the American 
Meekoceras beds, but this fauna shows, indeed, a strong kinship both 
with the fauna; of the lower and upper divisions of the Himalayan 
Lower Trias. Not less than twelve genera are common to both regions, 
namely, Meekoceras, Aspidites, Koninckites , Flemingiies, Xenodiscus, 
Ophiceras, Pseudosageceras, Hedenstroemia, Sihirites, Proptychites, 
Nanniies. Tirolites. 
There are equally close relationships with the fauna of the Meeko- 
ceras beds of the Himalayas and of the Hedenstroemia beds. There is 
a small number of very characteristic species, which point to a direct 
correlation with the Hedenstroemia beds. Hedenslrcetnia Mojsisovicsi 
is represented in America by R. Kosstnati, Pseudosayeceras inuUilobuturn 
by Ps. inter montanum, Flemingites Salya by Fl. cirrus. Among three 
species of Sibirites two are closely allied with forms from the Upper 
Ceratite limestone of the Salt Range. On the other hand the affinities 
with the Himalayan Meekoceras beds are at least equally close, and 
even with the fauna of the Ophiceras bed of the Otoceras zone in Spiti. 
