J. B. Hatcher — Geology of Southern Patagonia. 329 



and are supposed to represent the variegated sandstones (Areni- 

 seas abigarradas) of Carlos Ameghino ;* although both in this 

 region, and on the upper Rio Chalia they appear to be uncon- 

 formable with the overlying Dinosaur beds. 



The Guaranitic beds. — Above the barren sandstones there 

 is a series of variously colored sandstones and clays of immense 

 thickness, not less than 2000 feet, and in which there occur 

 in the greatest profusion the mineralized trunks of trees and, 

 less frequently, Dinosaurian remains. Dr. Ameghinof has 

 already called these beds the Guaranitica beds and referred 

 them to the Upper Cretaceous upon the evidence afforded by 

 the Dinosaurs found in them. The Guaranitic beds are well 

 represented on the head of Lignite creek on the south side of 

 Mayer basin, and on the upper Rio Chalia ; in both of these 

 localities they are much tilted and have a general dip to the 

 southeast. 



The Pyrotherium beds. — I mention here the Pyrotherium 

 beds and place them in the Cretaceous entirely upon the 

 authority of Ameghino. In my work on the Upper Rios 

 Chalia and Chico I was unable anywhere to identify the Pyro- 

 therium beds or to find evidences of the rich mammalian 

 fauna found in them by Carlos Ameghino. According to Dr. 

 Ameghino these beds immediately overlie the Dinosaur beds 

 and pass insensibly into them.;}; No difficulty whatever was 

 experienced in determining the Guaranitic beds and in find- 

 ing Dinosaurian remains in them. I searched faithfully these 

 Dinosaur beds from the base of the marine Tertiary above to 

 the barren sandstones below for mammal remains, but without 

 the slightest success. I never found in position in the Dinosaur 

 beds a single mammal bone or tooth. I did find mammal 

 remains in this region which seem to pertain to the genus Pyro- 

 therium, but they belong to a horizon much more recent than 

 the Guaranitic beds or even the Patagonian beds, and should 

 not be placed lower in the geological scale than Miocene, for 

 they are above the Supra-Patagonian beds of Ameghino. I 

 present here in fig. 1 an incisor tooth, No. 15101 in our collec- 

 tion, which from its size and shape appears to agree pretty 

 closely with the incisors of Pyrotherium. Only part of that 

 portion projecting from the jaw is preserved and this is nine 

 inches in length and nearly three inches in greatest diameter. 



* See "Note on Geol. and Pal. of Argentina," Geol. Mag., Jan., 1897, p. 5, 

 and Bol. Inst. Geografica Argentina, vol. xvii, 1896. pp. 87-108, and C. Amegh- 

 ino, " Bxpl. Geol. en la Patagonia," Bol. Inst. Geografica Argentina, vol. xi, 

 1890, pp. 1-46. 



f See F. Ameghino, ' : La Argentina al Traves de las Ultimas Epocas Geologicas ; 

 Imprenta de pabla E Coni e Hijos, Buenos Aires, 1897, p. 33. 



% F. Ameghino, Note on Geo], and Pal. of Argentina, Geol. Mag., London, 

 January, 1897, pp. 4-20. 





