ICHNOLOGY 



159 



and divergence is repeated throughout the entire series of the 

 present tracks. 



But what strikes the ichnologist, heretofore conversant 

 chiefly with the footprints of bipeds or quadrupeds, is the 

 occurrence in the present series of the third impression a, 



Fig. 64. 

 Protiehnites 7-notatw (Cambrian). 



which complicates the most approximated pair A, being placed 

 in front and a little to the inner side of the hindmost impres- 

 sion, a, of that pair. The superadded impression a, is about 

 the same size as the innermost in each pair, the average 

 diameter of that impression being 5 lines. 



Taking this view of the impressions, it appears that whilst 

 the innermost in each pair, a, b, c, are of equal size, the outer- 

 most, a", b\ c, 1 L, progressively increase in size, from the most 



