BY FRITZ NOETLIKG, M.A., PH.D., ETC. 17 



separal-ed by a sliarj) edge from the remainder of the sur- 

 face; it visually represents the highest part, of the Pollical 

 face, and inside the edge it is slightly concave. 



The longitudinal axis generally runs in the direction 

 of the blow, i.e., from the proximal to the distal end, and 

 the top coincides with the Pollical edge of the plane of per- 

 cussion. 



Inside the sharp edge there are sometimes faint con- 

 centric wrinkles, but they never extend beyond the edge. 



This is the "thumb mark" of the amateur collector, 

 and though there is no doubt that the thumb rested on the 

 fiat Pollical or Internal face, the scar of percussion is not 

 an intentional, but purely accidental feature. 



A combination of cone and scar of jjercussion is often 

 observed ; in that case the scar commences some distance 

 below the point of the cone, and the concentric wrinkles 

 run diagonally. 



5. RADIATING FilACTUKES OF PERCUSSION (R.P.) 



PL II , Fig. 8. 



On either side of the marks above described there ap- 

 pear frequently, though not always, short, closely set, 

 splintery fractures, radiating from the point of impact. 

 Sometimes they may also appear on the top cone, but they 

 are generally limited to both sides. It often hapjoens that 

 these radiating fractures ai"e the only signs of percussion on 

 the Pollical face, and then they are just as valuable in 

 determining the point of impact, and therefore the proximal 

 end, as any of the other marks. Professor Verworn was 

 the first who noticed these "Strahlen-spiiienge," as he calls 

 them, but a comparison of his figvire with a Tasmanian 

 tero-wattai seems to indicate that though due to the same 

 cause, the "ray fissures" are not quite identical with the 

 ' radiating fractures." Verworn's "ray fissures" are true 

 fissures radiating fi-om the point of impact apparently all 

 over the Pollical face; the "radiating fractures" of the 

 tero-watta are certainly not fissures ; on either side of the 

 cone, scar or wrinkles of percussion, close to the point of 

 impact, the surface does not flake smoothly, but the force 

 apparently produces a number of thin lamellae, which, by 

 breaking off, produce this peculiar feature. 



B 



