•2(> Windhausen— The Cretaceous- Tertiary 



with dinosaurs. In another section" 4 the Salamanca 

 Beds begin at the shore of the gulf in a normal position 

 above the Pehuenche and are overlain by the mammal- 

 bearing sediments ; for more than 30 miles inland, on the 

 west bank of the Rio Chico, the Salamanca Beds retain 

 the same thickness. 



Compared with Roca and Gualichu, the Salamanca sedi- 

 ments seem a little different ; a remarkable preponderance 

 of sands and clays and a decrease of the chalky corripo- 

 nent is apparent. Further, a special feature seems to be 

 the abundance of Ostrea pyrotheriorum, which is repre- 

 sented by a vast number of specimens and plays here the 

 same part as Ostrea ameghinoi in the northern half of 

 the San Jorge- Sea. 



As to the existence of Notostylops and Pyrotherium 

 Beds about the Gulf of St. George, it may be noted that 

 this region also belongs to the series in which contem- 

 poraneity of dinosaurs and mammals was emphasized by 

 Ameghino. 05 There can be no doubt that in the treat- 

 ment of this subject wrong inferences were drawn from 

 some partly correct observations. For the interpretation 

 of stratigraphic sections it is necessary to start from a 

 general base and establish harmony between strati- 

 graphic correlations, diastrophic phenomena and faunis- 

 tic movements. 



It has been demonstrated that the chief deposits of 

 dinosaur-remains are in the highest horizons of the 

 Variegated Sandstones, the marly-clayey formations of 

 the Pehuenche Beds. Whether it is assumed that the 

 bones are rolled (as Lydekker suggested) or relatively 

 in situ, is, therefore, a secondary question. The most 

 important fact is, that in Patagonia just as in other parts 

 of the world the dinosaurs became the most striking 

 element of the terrestrial faunas in the Upper Creta- 

 ceous. Nor is it improbable that at least certain groups 

 of this abundant reptile life survived the diastrophic 

 events at the close of Cretaceous time and even resisted 

 the invasion of the San Jorge-Sea, since large parts of 

 Patagonia remained outside of this transgression. We 

 can even imagine that some further biological evolution 

 affected the surviving remains of this fauna. Thus may 

 be explained the occurrence of dinosaurs at the base of 



04 Ibidem, p. 113, fig. 32. 



65 Les formations sedimentaires, p. 113, fig. 32. 



