50 



forms the rasping surface, which is only worked upwards. 

 The main portion of the shell during this process, therefore, 

 lies against the outer side of the palm. See ng. 64. 



Fig. 65. 



Fig. 64. 



When the point of a spear or other weapon is to be 

 sharpened, the prepared shell is held by the index and middle 

 finger of the right hand, so that the puncture is underneath. 

 The point of the weapon is then placed between the shell and 

 thumb, which latter presses the point against the shell, the 

 rasping being done only towards the body, in the direction 

 indicated by the arrow in fi^. 65. 



A strong bivalve shell (Cyrena essinytonensis) is also 

 used in the final process of chipping stone spearheads and 

 knives. The umbonal portion of the shell, with the convex 

 surface outwards, is held firmly by all fingers of the right 

 hand, in such a way that the ventral edge is away from the 

 palm of the hand. The latter border is pressed against the 

 chipped edge of the stone head, gripped by the left hand, and 

 by a careful wrenching of the right hand, in such a direction 

 that the thumb moves downwards, the requisite chipping is 

 accomplished. 



For this final process, a fragment of quartzite or flint is 

 often used, instead of the shell — that is, after the preliminary 

 flaking of the stone. This is used in the same way as the 

 shell. 



A bivalve shell is also used for cutting wood. For this 

 purpose the shell is held, dorsal surface upwards, between 

 thumb and middle finger, the index finger passing round the 

 umbo and convex surface. The ventral edge is placed against 

 the piece of wood, which is held with the remaining two fin- 

 gers. By combined pressure and half-circular forward 

 motions of the right hand the wood is cut through. See fig. 

 66. 



