6 F. Ameghino — Geology of Argentina. 



its almost horizontal beds slightly inclined to the east and not 

 exhibiting the least unconformity between each other. 



Although no fossil remains are yet known from this formation, 

 it is almost certain that it ought to be referred to the Lower or 

 Middle Cretaceous, since the deposits which rest immediately upon 

 it belong to the Upper Cretaceous. In fact, at various points, e.g., 

 on the Senguel, the Deseado, etc., above these variegated sandstones 

 and in concordant stratification, there comes another formation of red 

 sandstones, a little more friable but also of great thickness and con- 

 taining a considerable quantity of bones of gigantic Dinosaurs. 

 These deposits constitute a vast formation which extends from one 

 end of Patagonia to the other, since it has been observed from the 

 Eiver Negro and the Neuquen to the north, as far as San Julian and 

 Lake Argentina to the south, always with the same characters, 

 everywhere containing remains of Dinosaurs and a remarkable 

 quantity of petrified wood ; large complete trunks are continually 

 observed still standing in their natural position. 



That this formation is Secondary, is clearly indicated by the 

 Dinosaurs ; on the other hand, as its upper beds pass insensibly 

 into another formation, which contains numerous remains of mammals, 

 it cannot be doubted that the sandstones with Dinosaurs belong to 

 the Upper Cretaceous. Mr. Lydekker has given a description of the 

 Dinosaurian remains from this formation preserved in the Museum 

 of La Plata.-' The species which has left most remains belongs, 

 according to him, to the genus from the Cretaceous of India which 

 he had previously described under the name of Titanosaunis, and he 

 terms the Argentine species Titanosaurns australis. This conclusion 

 w^ould be indisputably of great importance, but I have my reasons 

 for doubting the generic identity'. The other remains are described 

 under the names of Titanosaurns nanus, Lyd. ; Argyrosaurus superlms, 

 Lyd., one of the most gigantic colossal animals which have trodden 

 the earth ;^ and Microcoelus Patagonicus, Lyd. 



The author observes that until his memoir no representative of 

 this group from the Argentine Eepublic had been described, but 

 that C. Burmeister had published some preliminary notices of them. 

 These notices, published in the year 1893,^ are confined to the 

 indication of having met with remains which he supposes to be 

 Dinosaurian — remains whose occurrence in Patagonia had already 

 been reported by Carlos Ameghino.* There is also a lack of 



1 E. Lydekker, "The Dinosaurs of Patagonia" : Anal. Mus. La Plata — Pal. 

 Argent., vol. ii, 1894, pt. 1. 



^ The gigantic fore-limb of this animal, -which serves as the tj'pe of the genns and 

 species, -was discovered by Carlos Ameghino, together with the almost complete 

 skeleton in position, at the angle which the Eiver Chico makes with Lake Musters 

 (see F. Ameghino, " Contrib. conoc. mamif. fos. Eepub. Argentina," 1889, p. 879; 

 and C. Ameghino, Bol. Inst. Geogr. Argent., vol. xi, 1890, p. 42). Unfortunately, 

 the incompetent persons employed by the Director of the Museum of La Plata for the 

 exhumation of this skeleton only succeeded in extricating one of the limbs, destroying 

 the remainder. The traveller who has occasion to cross this district still descries 

 Ixom a great distance the accumulation of bones destroyed by their vandal expedition. 



3 Eevista del Museo de La Plata, vol. iv, 1893, pp. 245-6. 



* Carlos Ameghino, Bol. Inst. Geogr. Argent., vol. xi, 1890, pp. 42, 44. 



