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



It is true that Dr. Florentine) Ameghino states that the 

 variegated sandstones of the interior extend to the Atlantic 

 coast, and are covered in concordant stratification by the same 

 strata with Pyrotherium • but since he gives no localities and 

 nowhere describes any remains of Pyrotherium or other mam- 

 mals from those beds as having been found at San Julian or 

 other localities on the coast, the correct identification of those 

 beds as Pyrotherium may well be questioned. 



I have dwelt at some length upon the question of the age 

 of the Pyrotherium beds because of the importance of the 

 problems involved. If the beds containing this remarkable 

 mammalian fauna be really Cretaceous, not only may the value 

 of vertebrate fossils as means of correlation be seriously ques- 

 tioned, but a very decided blow will also be struck at the 

 validity of all correlations based on paleontological evidences, 

 whether of vertebrates, invertebrates or plants. 



Until this entire region has been carefully explored and the 

 stratigraphic position of the Pyrotherium beds accurately de- 

 termined, by men trained in stratigraphic work, the question 

 of their exact position in relation to the Dinosaur beds and to 

 the different Tertiary beds, as well, will remain unsettled in 

 the minds of most vertebrate paleontologists. 



Tertiary Deposits — Eocene. 



The Patagonian beds. — Extending along the Atlantic coast 

 in an almost unbroken succession from New Bay on the north 

 to near the mouth of the Coy Piver on the south, there is a 

 series of light-colored, well stratified sandstones and clays, 

 usually quite soft but sometimes, especially in the sandstone 

 layers, enclosing very hard, lenticular concretions. These beds 

 are known as the Patagonian beds, and the typical locality for 

 them may be considered as the Atlantic coast anywhere from 

 Port Desire to the mouth of the Santa Cruz Piver. They 

 attain to a thickness of several hundred feet, are of marine 

 origin and are everywhere characterized by marine inverte- 

 brates in great abundance. In the region south of Port Desire 

 they dip very gradually to the southeastward, so that their 

 uppermost strata disappear beneath the waters of the Atlantic 

 about midway between the Santa Cruz and Coy Rivers. 



In regard to the age of the Patagonian beds there has been 

 great difference of opinion, but most persons acquainted with 

 them and with the invertebrate fauna found in them agree in 

 referring them to the Eocene. Dr. Ameghino, in discussing 

 this question, says :* " The fact is that the Patagonian forma- 

 tion begins with the Upper Cretaceous, but acquires its great- 



* See Notes on Geol. and Pal. of Arg , p. 12. 



