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prensa ARCHEOLOGY IN BRITISH GUIANA oi 
Ficure 17.—Percussion-made pestles of the Alaka Phase showing surfaces worn by grinding. 
shale. Two fragments were found at N-8, both of which probably 
had a rectanguloid shape when complete. The larger, made of pol- 
ished shale, measures 5.3 cm. long by 3.6 cm. wide. One edge is highly 
polished to a sharp cutting edge and the opposite end flattened and 
smoothed (fig. 18,d@). It is split lengthwise so the existing thickness 
is only 8 mm., but the original thickness must have been at least 1.5 
cm. The other artifact is smaller and more fragmentary, measuring 
3.2 cm. long, 2.8 cm. wide, and 5 mm. thick. 
