PALEOZOIC AND MESOZOIC BORDER-LINE 521 



the lower Ceratite limestone and that of the Ceratite marls are 

 so similar that a separation of the two is out of the question, 

 and even the genus Otoceras is found in the latter. Now, since 

 these doubtful beds are younger than any accepted Permian, and 

 older than any authentic Trias, they might with equal propriety 

 be assigned to either, and we shall have to extend one or the 

 other system to include them. The question will have to be 

 decided either by paleontologic relationship, or by priority of 

 reference. The Otoceras beds contain Meekoceras, Proptychites, 

 Ophiceras, and several other ammonite genera that have never 

 been found in the Paleozoic ; they contain also Medlicottia and 

 Otoceras that are more characteristic of Upper Permian ; but they 

 lack the Productidae and Orthidae that characterize the Permian 

 formation. Thus the paleontologic evidence is about equal in 

 favor of a reference to either Paleozoic or Mesozoic. But the 

 geologists that described the fauna of the doubtful beds have 

 almost unanimously referred them to the Lower Trias, and this 

 must be the final verdict. 



The fauna of the Meekoceras beds of Idaho and California is 

 most intimately related to that of the Ceratite marls and the 

 lower part of the Ceratite sandstone of India, with most of the 

 genera in common, and several species that seem to be identical. 

 And although the writer has searched carefully for Otoceras in 

 both places, no trace either of this genus or of Medlicottia was 

 found. It seems likely, then, that even if the bottom of the 

 Ceratite formation should be cut off from the Trias and assigned 

 to the Permian, this change would not affect the nomenclature 

 of our American formations that are now considered as the bot- 

 tom of the Mesozoic series, and the Meekoceras beds will stand 

 as the type of the marine Lower Trias, where White and Hyatt 

 placed them in 1879. The real transition from Paleozoic to 

 Mesozoic must be sought in the conformable series below the 

 Meekoceras beds, and above the Fustdina limestone. 



James Perrin Smith. 



Stanford University, 

 California. 



