C. A. White—Jurassic Strata of North America. 231 
specimens are not numerous and perfect, and the incidental 
evidence is conflictin i 
forms, the latter constituting the more distinctive feature of 
that fauna. On the contrary, not one of those, or any other 
distinctively Cretaceous types has ever been found in our Juras- 
Sle strata at any of the many hundreds of localities, extending 
ver many thousands of square miles, at which fossils have 
been collected from it. And our Jurassic molluscan fauna is 
also very constant in its character at all the places where it 
has been found. Furthermore, Mr. Whiteaves does not claim 
‘0 have discovered any of our Jurassic Ammonitide, nor Ju- 
Although I do not regard the evidence which Mr. Whiteaves 
has Presented as at all supporting his position, there a “1 
“ircumstances which apparently favor the doubt which t : 
Publication of his views may have raised as to the true age 0 
the formation which we have always regarded as Jurassic. 
