Wilckens takes all of this series, from the base of the Salamanca, up to the unconformity below the Patagonian, and makes of it his St. George Period, a transgression epoch, lasting to the end of the Upper Cretaceous. I believe it is all marine, and is all a part of the Upper Cretaceous transgression of the sea over Patagonia. However the Salamanca is a clear cut deposit and I feel it should be retained as a distinct horizon. The overlying light colored (white, grey, brown, yellow, or green) sandy clay shales represent a deeper water and later facies, which is characteristically developed on the Gulf of St. George, and may well be distinguished as the St. George epoch or series, but I should use the term only in this more limited way. It is the same series which Ameghino has plotted as the Notostylops beds on his section of the coast of Patagonia. This last it certainly is not. The unconformity between these white (or light) sandy clays and the Patagonian represents a regression period, during which Patagonia was not only above water, but extended an unknown distance further to the East. It was during this interval of time between the Upper Cretaceous and the Lower Miocene (Patagonian) that the limited and local land deposits known as Casamayor (= Notostylops), the Astraponotus, and the Deseado (= Pyrotherium) and probably other beds were laid down. In each case the age must be determined for the individual bed by its contents mostly; for as far as I know none of them overlap anywhere. In regard to the discussion as to whether Dinosaurs were contemporaneous in South America with the fauna of the Deseado, I can only say, we found no trace of a dinosaur or any other Cretaceous animal in the Deseado beds which we worked. As the Cretaceous beds lie as high as the Deseado and are also practically horizontally striated, dinosaur remains might be found on the same level. I think the assigning of any such material to these beds was due to failing to recognize the unconformity under the Deseado beds. As to the Notostylops fauna and dinosaurs being contemporaneous, I only worked the Notostylops beds at Mazaredo, but there I found nothing to indicate the contemporaneousness of these two groups. As I have shown above, Ameghino’s idea of the extent of the Notostylops or Casamayor beds was mostly at fault, and very much of that which he has designated as of Notostylops age is Upper Cretaceous. It is in these Upper Cretaceous beds that dinosaurs do occur and this seems to me to be the basis of the confusion. This Upper Cretaceous series is a field where considerable work may profitably be done, in straightening out the relationships of the various layers to each other, their extent, and their relationship to the Salamanca and other Upper Cretaceous formations in other parts of Argentine.