hedliCka] skeletal EEMAINS OF EARLY MAN 271 



leeward of the hollow, the prevailing winds of the region being from 

 the south or southeast, and the southern scarp of the ridge exhibits 

 effects of wind erosion. It is evident that the material of the hill 

 was blown out of the hollow. 



An examination of the material composing the hill shows that it 

 differs in structure and firmness from the Pampean terrane of the 

 plain. It is a perfectly homogeneous fine-grained loess, which is 

 devoid of stratification. Wlien damp it is light-to-medium brown, and 

 dries out whitish to pink. Films of a white calcareous deposit ramify 

 all through it and grit against the knife, but there are no distinct lime 

 concretions or tosca. The material of the Pampean terrane, which 

 forms the plain and in which the hollow is excavated, is precisely 

 similar in fineness of grain, but is darker colored and more compact. 

 Wlien blown into dust it would yield the loess of the hill. 



The writer was accompanied over the ground by D. Cesar Pirez, 

 the majordomo of the estancia, who stated that in sinking a well, 

 which is marked by the windmill that may be seen in the photo- 

 graph (pi. 27), there was first penetrated the black superficial soil, 

 then 2 m. of loess, and below this again black soil about 30 cm. thick, 

 overlying the brown earth of the Pampean terrane. The well is 

 located below the summit of the ridge at an elevation which probably 

 does not exceed 2h or 3 m. above the general level of the plain, and 

 it is thus reasonably certain that the loess of the ridge lies upon the 

 black soil of the plain, which was buried as the loess dune formed. 



The conditions under which such a dune may form depend on the 

 existence of a steep accident in the surface. The wind, sweeping 

 across a hollow, is diverted upward in striking a steep bank on the 

 farther side and forms an eddy at the summit of the bluff. In this 

 eddy sand or loess is deposited. The winding hollow resembles an 

 erosion channel and the development of the dune was occasioned, 

 according to the writer's understanding of the circumstances, by the 

 abandonment or drying up of the stream channel which it represents. 



According to this interpretation the ridge is a local feature which 

 has been built upon the plain in comparatively recent time. 



Upon the summit of this ridge, about the highest point, were found 

 the human remains which C. Ameghino excavated. The exact spot 

 is indicated in the photograph (pi. 28), directly beneath the figure 

 of Senor Pirez. The hole was partially refilled but may be easily 

 distinguished. According to Senor Pirez and judging from the posi- 

 tion of the hole, the body lay on the southern slope, about 2 m. 

 below the highest level of the plain, but covered by not more than 

 half a meter of brown earth in place. The body lay with the head to 

 the north, the feet toward the south, and in a somewhat inclined 

 position. The head remained at a slight distance from the rest of the 

 body, which seemed to have slid down the hill. Senor Pirez remarked 



