AGE OF THE LAKAMIE DEPOSITS. 203 



of the Cretaceous series, the Maestriehtian,'" are carried in the Wesst- 

 ern Tenitories of the United States to a horizon probably considera- 

 bly higher, the Laramie, whose position is now generally recognised 

 as Post-Cretaceous. Indeed, if the reported association in these beds 

 of one of the Hadrosauridre with the remains of the mammalian Me- 

 niscoessus be taken in its full value, we may not unreasonably as- 

 sume this fact to be further evidence, in addition to that which has 

 already been adduced, in favour of uniting at least a portion of the 

 Laramie with the Eocene. Surely the circumstance that dinosau- 

 rian remains are found in these deposits is not of itself, as against 

 all other evidence, sufficient to establish the age of the formation. 

 What is there that we know of that should prevent the animals of 

 this group from continuing up into the Eocene, any more than the 

 Carboniferous and Permian labyrinthodonts into the Trias, and the 

 Cretaceous Crocodilia into the Tertiary ? It is not to be supposed 

 that a common catastrophe awaited all the members of this numer- 

 ously-represented order of animals, when by their organisation they 

 seem to have been fitted to such varying conditions of environment. * 



* Were these reptilian remains the only fossils of a distinctive character 

 found in the Laramie formation, then, naturally, we should conclude that the 

 formatioa in question was of Cretaceous age ; at least, the only evidence we 

 had would be in favour of such a conclusion. But the case, as it here stands, 

 is quite different. The fossil plants of the Lignite, as is well known, are al- 

 most altoffetlior of Tertiary types, and many of the species, even, have heen 

 identified, by Starkic Gardner, Lesquereux, and others, with characteristic 

 Lower Tertiary forms occurring in various parts of Europe (Island of Sheppcy, 

 &c.). The shell-fauna, as a whole, can scarcely be said to approximate very 

 much more to the one side than the other, although a few species have heen recog- 

 nised by hotli Conrad and Meek as being more nearly Tertiary than Cretaceous. 

 These, however, do not indicate much. The recent discovery of Meniseoessus 

 adds a much more powerful link to the evidence which favours the Tertiary side 

 of the question ; indeed, by itself it argues about as much for the Tertiary age of 

 the formation as the reptilian remains do for the Cretaceous, for, were there no 

 such conflicting testimony as in reality exi^ts, its evidence would be accepted 

 as conclusive. Further evidence in this direction is afforded by the reptilian 

 genus Champsosaurus, which, as a member of a fauna, the Pueroo, origmally 

 supposed to represent the Laramie, has been identified as an Eocene genus in 

 the north of France. While, perb"ps. it may be admitted that paleontology has 

 not thus far given us absolute data by which to determine the question at issue, 

 yet, on the whole, its facts appear to lean more towards the Tertiary side. From 

 stratigraphy we learn but little, as, imfortunately, marine deposits of Post-Cre- 

 taceous age are wanting in the interior of the continent, thereby rendering ths 



