Lisboa — Pebbles on the Central Plateau of Brazil. 15 



weather action, having its depressions full of microscopic vege- 

 tation. 



(e) No. 8 seems to show by its shape that it was 

 formed from a common rounded stone, and it still preserves 

 much of its primitive form. The remarkable feature of this 

 stone is a concave face which is quite as polished as the convex 

 one and it is also full of pits and vegetation. The base is 

 rough but sufficiently plane to stand firmly. The rounded out 

 edge of the bottom clearly shows the line of division between 

 the part that was sunk into the clay and the part exposed. 



(/') The pebble shown in No. 9 is a facetted wedge- 



Facetted pebbles from the central plateau of Brazil. 

 About half the natural size. 



like stone that has been polished on all its faces except on the 

 smallest one, which looks as if it had been chipped off. Only 

 one of its facets is convex and probably represents the remain- 

 ing part of what was formerly a common water-worn pebble. 

 All around the pebble is a line which seems to show the strati- 

 fication of the rock, which is perpendicular to the chipped 

 side. The pits on this sample are not so developed as on the 

 three above described. On the bottom edge there is an irregu- 

 larity resembling a broken lip, half resting on the polished 

 convex face and with equally polished edges. On one of the 

 polished flat faces can be noticed slight cavities that indicate 

 friction from another hard body. On this sample can also be 

 observed the distinctive coloring of the zone that was under 

 the clay and the one exposed to the weather. 



