Boundary in South America. 29 



outlet to the sea, and the essential part of this section 

 consists of marly sands and clear sandstones with inter- 

 calations of clay. The boundary between the Salamanca 

 and the overlying terrestrial deposits is formed, accord- 

 ing to Stappenbeck, by a sheet of black bituminous clay. 

 As to the Casamayor and Deseado Beds, this author has 

 given two sections. One of these is identical with the 

 classic section from the southern shore of Lake Colhue 

 Huapi, published by Ameghino, while the second one is 

 the continuation of the alleged section of Rio Chico and 

 comprises a complex of crossbedded yellow and green 

 sands, sandstones and clayey intercalations, which may 

 be about 300 feet thick. 



The work of the Amherst Expedition to Patagonia has 

 been extraordinarily successful in a paleontologic sense, 

 and a rich collection of the so-called Pyrotherium fauna 

 was obtained in a locality 3 miles east of Rio Chico and 

 to the west of Puerto Visser. Loomis published two 

 typical sections that comprise deposits of the Salamanca, 

 of the overlying terrestrial horizons and even of the 

 Patagonian Formation. As to the interpretation of 

 these sections I do not agree entirely with Loomis. In 

 the chief section of the so-called "Deseado exposure," 

 this writer laid emphasis on the existence of an uncon- 

 formity between the terrestrial deposits with Notosty- 

 lops and Pyrotherium and the overlapping Patagonian 

 Formation; but in the other two sections he did not 

 distinguish the marine fossil-bearing Salamanca from 

 the overlying terrestrial sediments which according to 

 him contain turtles, fossil wood and "fragments of some 

 sort of a bone." As the name "San Jorge-Formation" 

 was created by Wilckens only for the marine deposits 

 between the previously mentioned limits, the sections of 

 Loomis cannot be assigned entirely to the San Jorge. 

 The middle parts of the sections A and B belong to the 

 Notostylops and Pyrotherium Beds, and the section of 

 figure 2 is identical with the section published by Ame- 

 ghino in "Les formations sedimentaires," p. 113. 72 

 It seems to me a feature of special importance that in 

 the two sections A and B the terrestrial deposits rest 

 upon apparently different levels of the marine Sala- 

 manca, and in each case Loomis gives a separate list of 

 fossils, although all the specimens belong without excep- 



72 See Carlos Ameghino, Le Pyrotherium, 1 'etage Pyrothereen et les 

 couches a. Notostylops, Un reponse a Mr. Loomis. Eevista "Physis," vol. 

 1, No. 7, Buenos Aires, 1914. 



