Boundary in /South America. 23 



the variegated Keuper-like marls of the so-called Pehu- 

 enche Beds (Piso Pehuenche, Doering and Ameghino), 

 which may be considered either as the highest part of 

 the Variegated Sandstones of the Upper Cretaceous 

 (Areniscas Abigarradas) or perhaps as basal formations 

 of the Roca Beds. In these strata, Dr. Wichmann col- 

 lected in 1912, on the southern shore of the Rio Negro, 

 a nearly complete dinosaur skeleton, now in the National 

 Museum at Buenos Aires. 54 According to a communica- 

 tion from Carlos Ameghino, this skeleton does not belong 

 to a Titanosaurus, as has been assumed before, but to a 

 Sauropod of the family of the Diplodocidce. 



Florentino Ameghino claimed that remains of Pyro- 

 therium and dinosaurs had been found in the same layer, 

 nearby in the region west of the junction of the rivers 

 Neuquen and Limay, thirty miles west of Roca. 55 This 

 association of dinosaurs and mammals was one of the 

 chief supports for a Cretaceous age of the ancient Pata- 

 gonian mammalian faunas. A priori it is necessary to 

 call attention to the fact that this report is to be judged 

 in the same manner as the unfounded statement that 

 ammonites occur at Roca. 56 With regard to the alleged 

 occurrence of dinosaurs and mammals to the west of 

 Confluencia (junction of Rio Neuquen and Limay) an 

 exact statement about the locality has never been made. 

 Lydekker 57 as well as Smith Woodward 58 have turned 

 their attention exclusively to the paleontologic side of this 

 matter, without going into studies of a stratigraphic 

 kind. As the Roca-Sea never invaded the region to the 

 west of Confluencia, it is obvious that the mammal-bear- 

 ing Chichinales Beds in the lower course of the Rio 



64 See Wichmann, Las capas con Dinosaurios en la costa Sur del Eio 

 Negro f rente a Gral. Eoca, Revista ' ' Physis, ' ' vol. 2, pp. 258 etc., Buenos 

 Aires, 1916. 



55 L 'age des formations sedimentaires de Patagonie, pp. 19, 20 of the 

 abstract. — Les formations sedimentaires, p. 77. See also on the same sub- 

 ject: Wilckens, Die Meeresablagerungen etc., pp. 151, 152. 



50 These ammonites really came from the Upper Jurassic beds in the 

 Preandine zone (Cerro Lotena) and had been mixed with collections from 

 Roca, due to the inexperience of the collector. There can be no doubt that 

 the same occurred with the bones of dinosaurs and of Pyrotherium from 

 different localities and horizons. 



57 Contributions to a knowledge of the fossil vertebrates of Argentina, 

 Anales del Museo de La Plata, Paleontologia Argentina, 2, La Plata, 1893. 

 Supplemental observations on the extinct ungulates of Argentina, ibid., 3, 

 La Plata, 1895. 



53 On two Mesozoie crocodilians, Anales del Museo de La Plata, Paleon- 

 tologia Argentina, 4, La Plata, 1896. 



