786 JAMES PERRIN SMITH 
can Trias, based on the published writings of Gabb, Meek, 
Hyatt, Whiteaves and the writer, and upon personal communi- 
cations from Hyatt and the writer. Mojsisovics here takes 
the view that the occurrence together of the Subbullatus fauna 
and Tyrachyceras in India and California shows a survival of the 
latter group beyond its time elsewhere; this is more likely true 
of India, where the survival consists of single species of genuine 
Trachyceras, but in California the fauna is almost too large to be 
a survival. 
The most interesting fact brought out by a comparison of 
the Upper Trias of California with that of India and the Alpine 
Mediterranean region is its near relationship with the latter, 
most genera and many species being common to the two 
regions. On the other hand, not many genera and no species 
are now known to be common to California and India; this is 
contrary to what we should expect, knowing that during the 
Lower Trias California was closely connected with India, as 
shown by community cf genera and possibly of species, and also 
that during this same time neither India nor California was closely 
connected with the Mediterranean Triassic sea. Great changes 
in physical geography must have taken place about the end of 
Lower Triassic time, of which we have a partial record; during 
the Muschelkalk several species are common to the Indian, the 
Arctic-Pacific, and the Mediterranean regions, thus showing an 
opening of connection between regions that before were separated. 
This relationship of the Californian to the European faunas 
persists until after the middle of the Jurassic formation, when the 
Boreal fauna comes in; towards the end of the Lower Cretaceous 
the connection with India is again established. 
It is hard to see how anyone that has studied the changes of 
faunal geography undergone by the western American region 
since Paleozoic time could believe in the permanency of the 
oceanic basins as they now exist. These shifting faunal relations 
can only mean rising and sinking of continental margins, cutting 
off and facilitating intermigration, alternately aiding and obscur- 
ing interregional correlation. JAMES PERRIN SMITH. 
