ON THE DISTRIBUTION OF LOWER TRIASSIC FAUNAS* 
JAMES PERRIN SMITH 
Leland Stanford Jr. University, California 
No formation has added more in recent years to our knowledge of 
ancient faunal geography than the Lower Triassic. In this epoch 
we now know three distinct and widely distributed interregional 
faunal zones, which are truly bench-marks in correlation. These 
are in sequence upward: (1) the Meekoceras zone; (2) the Tirolites 
zone; (3) the Columbites zone. They do not have the same distri- 
bution, nor are the relationships of the various regions constant for 
the successive epochs, showing that there was considerable change 
in physical geography during the Lower Triassic. Critical studies 
of these faunas from Siberia, India, Madagascar, the Indian 
Archipelago, and western America have made it possible for us to 
understand the ancient faunal geography in a way that was impos- 
sible a few years ago. 
FAUNAS OF THE MEEKOCERAS ZONE 
The Meekoceras fauna of Madagascar.—During the past year 
Dr. H. Douvillé? has announced the discovery of the Meekoceras 
fauna on Madagascar; with Meekoceras cf. gracilitatis, Flemingites, 
Cordillerites, and Lecanites, all closely allied to species in the Ameri- 
can fauna. This argues for a connection during this epoch between 
the Great Basin Sea and the Indian Ocean. Madagascar and the 
Great Basin of western America are almost exactly opposite each 
other on the globe, and the distance would be about twelve thousand 
miles by a great circle. From the Great Basin to Madagascar 
around the old shore line of the North Pacific, and then down the 
Asiatic coast and around the old shore line of the ancient Australa- 
sian land-mass, would be about twenty-one thousand miles. But 1 
Published by permission of the Director of the U.S. Geological Survey. 
2 Compt. rendus. Acad. Sct., 1910, p. 210; and Bull. Soc. géol. France, 4° sér., Tome 
>. 0) oan 
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