288 BUREAU OF AMERICAN ETHNOLOGY [bull. 52 



1 or 2 meters due to wind erosion/ and that the softer, as already 

 stated, has been deposited in the hollows (see pi. 29). 



It was in the softer of these two deposits that the skeletons were 

 found, and it was in similar formation in another part of the plaj^a 

 that part of a carapace of a Glyftodon munizi was observed by 

 Hrdlicka and the writer. Neither the skeletons nor the remains 

 of the glyptodon appear to have any relation to the formation as 

 fossils indigenous to it. 



A formation which is possibly younger than the sandy softer 

 facies of the Inter-Ensenadean is a layer of sandy black earth, 

 which in some places is probably the soil of the pampa where the vege- 

 tation has been destroyed by advancing sand dunes, and elsewhere is 

 an eolian deposit blown out from the pampa and mingled with sand 

 and broken shells. Ameghino assigned it to a Recent date. It con- 

 stitutes the floor of smooth flat hollows among the sand dunes, to 

 wliich the name ''black pla^^as" was applied. Quantities of dripped 

 stones were scattered over these playas.^ About a dozen large and 

 small exposures of the formation in a range of 7 kilometers along 

 the coast were examined, but no fossil bones of extinct animals were 

 seen, although bones of ostriches and of modern domestic animals 

 were not uncommon. 



Capping the black-soil layer are dunes composed of brown-to-gray 

 sand, wliich are overgrown with grass and fixed. They form an inner 

 zone of low mounds on the margin of the pampa and sink away 

 inland on the plain, ^^lere they are eroded and exposed in sections, 

 their relation to the underlying black soil is plainly to be seen. 



The latest formation in the district is that of the great sand dunes 

 which rise to a height of 20 to 25 meters. These consist of marine 

 sands, shells, and some loess, blown up by the southerly winds. 

 They are in constant motion. Their distribution wdth reference to 

 one another is determined by the interaction of the winds from the 

 south or southeast, that build them up and move them, with the 

 winds from the northwest that blow across them. The latter tend 

 to maintain open passes across the broad zone of moving sand hills, 

 and thus prevent the constructive winds from building up con- 

 tinuous ridges. It was in one of these passes through the zone of 

 sand dunes that the two skeletons were found together. 



The writer regards the moving sand, the older dunes, the black 

 soil, and the brown sandy faces of the Inter-Ensenadean, all as 

 Recent formations, on the ground that they are all related to the 

 phenomena of the coast and owe their genesis to the erosive or con- 

 structive activities of the winds. The harder facies of the Inter- 



1 See Doctor Hrdlicka's account. 



' Similar worked stones, chips, etc., " black" and "white," were found scattered over tlie flat in which 

 were discovered the two skeletons. 



