J. B. Hatcher — Geology of Southern Patagonia. 335 



est development during the Eocene. The fossiliferous deposits 

 of Qniriquina were at first regarded as Tertiary, and were only 

 assigned to the Cretaceous after there had been discovered in 

 them remains of Plesiosaurus (Cimoliosaurus) chilensis, of 

 Ammonites, and some other Secondary genera. 



" The late Cretaceous formation of the coast of Chili ex- 

 hibits absolutely the same aspect and the same lithological 

 characters as the Patagonian formation. The facies of the 

 fauna is equally the same, since the Cretaceous fauna of Quin- 

 quina only differs from the fauna of the Patagonian forma- 

 tion by the presence of eight genera (Ammonites, Hamites y 

 _B acuities, Pugnellus, Cinulia, Pholadomya, Monopleura, 

 Trigonia), which are not met with in this latter ; while 85 

 per cent, more or less, of the genera of the Cretaceous forma- 

 tion are also found in the Eocene Patagonian formation. 

 Moreover according to Philippi, the best authority on the sub- 

 ject, 20 per cent of the species of shells of the Cretaceous for- 

 mation of Algarroba are likewise species of the Patagonian 

 formation, and it will be recognized that in Patagonia the 

 marine Cretaceous and Eocene formations pass from one to 

 the other in a gradual and insensible manner." 



Granting that the facts as stated above are correct, and Dr. 

 W. Moericke* has shown that considerable doubt exists as to 

 the above association of species at the localities mentioned, 

 they do not justify Dr. Ameghino's conclusion that the Lower 

 Patagonian beds belong to the Upper Cretaceous ; for in regard 

 to the eight genera mentioned above as found only in the 

 Cretaceous of the west coast and not in the Patagonian beds, 

 it should be remembered that of these, six are characteristic 

 of the Mesozoic, and are unknown in any deposit later than 

 Cretaceous, while the two remaining, Pholadomya and Tri- 

 gonia, are found indiscriminately from the Lias to recent 

 times. The per cent of genera or even of species common to 

 the two deposits is of less importance than the character of the 

 genera and species peculiar to each. Now six of the eight 

 genera found in the Cretaceous deposits of the west coast and 

 absent in the Patagonian beds are typical Mesozoic genera, 

 while most of those genera found only in the Patagonian beds 

 are unknown from the Cretaceous, and the greater number of 

 genera common to both have been found in different localities 

 throughout the world in both Secondary and Tertiary deposits, 

 and are therefore unimportant in determining the age of either 

 series of beds. If the Lower Patagonian beds really belong to 

 the Cretaceous, since they are of distinctly marine origin, we 

 should find in them some trace of that unusually prolific Ce- 

 phalopod fauna (Ammonites, Hamites, Scaphites, Baculites, 

 * Neues. Jahrb., etc., Beil. Bd. x, 1896, p. 594. 



