6 PATAGONIAN EXPEDITIONS PALAEONTOLOGY. 



horizons that Mr. Hatcher has recognized in the Pueyrrydon series. The 

 fact that the species found in each of the three horizons appear to be 

 peculiar to it would indicate different epochs if each horizon yielded 

 enough species to constitute a real fauna. But the Gio beds yielded 

 only a single species of Ostrea which is occasionally bored by a Litho- 

 pliagns and the lower conglomerate contained only the small Turnus 

 diibins boring in fossil wood. These are all forms that would not seem 

 out of place if immediately associated with the fauna of the overlying 

 Belgrano beds and probably do not differ greatly from it in age, the 

 vertical distribution of species in this part of the section being due rather 

 to local conditions than to great faunal changes. This conclusion is in 

 harmony with Mr. Hatcher's observation that the beds are conformable. 

 In attempting to correlate this series with horizons that have been es- 

 tablished elsewhere the natural course is to begin comparisons with for- 

 mations described in adjacent regions, or at least on the same continent, 

 but the data for direct comparisons are almost wholly lacking. It will, 

 doubtless, be a surprise to the reader, as it was to the writer, to find that 

 no previously described species is recognized in this collection from 

 southwestern Patagonia. This is the more surprising for the reason that 

 the Cretaceous is known to be widely distributed and represented by 

 many horizons in South America. It covers considerable areas in Brazil 

 where it has yielded a large fauna described by White 1 but the facies is 

 entirely different from that of the Cretaceous of Patagonia, if indeed, the 

 same horizons are represented. Along the western Cordillera, both 

 Upper and Lower Cretaceous fossils have been described or reported from 

 many areas extending from Venezuela and Colombia to the Strait of 

 Magellan and as Mr. Hatcher's localities are in this western belt, it was 

 naturally expected that many of the species would be referable to de- 

 scribed forms. A careful examination of the literature describing South 

 American Mesozoic fossils failed to reveal a single species with which any 

 of the fossils here described can be positively identified. It should be 

 remembered in this connection, however, that none of the collections 

 previously described was obtained within several hundred miles of Lake 

 Pueyrrydon, and that, with few exceptions, the collections were small and 

 not really representative of the faunas. In a few cases species that I 



1 Contributions to the Paleontology of Brazil. Archivos do Museu Nacional do Rio Ja- 

 neiro, Vol. VII, 1887. 



