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- 
phagus and the lower conglomerate contained only the small Timms 
dubius 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. 
