12 IAsboa — Pebbles on the Central Plateau of Brazil. 



of the polyhedron, the other facets being polished and shiny 

 with a general tendency towards convexitj 7 . The polished sur- 

 faces are sometimes quite smooth ; at other times they are cov- 

 ered with small holes, reminding one of small pock-marks. 

 The pebbles may be grouped under two general divisions: 

 1. The pyramidal type. — To this type belong six of the 

 samples, (a) Numbers 1, 2, and 3 are distinguished by their 

 elongated shape. They are 8 or LO centimeters long, 6 or T 



2a 



3a. 



Facetted pebbles from the central plateau of Brazil. 

 About lialf the natural size. 



broad and 3 or 4 high. Two of them have a rough base, full 

 of holes. This, in the most perfect or regular sample, shows 

 three sharp edges joining the three polished facets. In num- 

 ber 3, only the top edge is well defined, uniting two facets 

 which are separated on the other side by a curved facet with 

 undefined edges which seem to have been worn out. Two of 

 these specimens have the base rough, full of holes and suffi- 



