DISCOVERED AT KIRKDALE, IN YORKSHIRE. SI 
collected and carried away since the cave was discovered. The degree 
of decay is always equal in the teeth and portions of jaw bones to 
which they are attached. 
In many of the most highly preserved specimens of teeth and 
bones there is a curious circumstance, which, before I visited Kirk- 
dale, had convinced me of the existence of the den, viz. a partial 
polish and wearing away to a considerable depth of one side only; 
many straight fragments of the larger bones have one entire side, or 
the fractured edges of one side, rubbed down and worn completely 
smooth, whilst the opposite side and ends of the same bone are sharp 
and untouched, in the same manner as the upper portions of pitching 
stones in the street become rounded and polished, whilst their lower 
parts retain the exact form and angles which they possessed when 
first laid down. This can only be explained by referring the partial 
destruction of the solid bone to friction from the continual treading 
of the hyaenas, and rubbing of their skin on the side that lay upper¬ 
most in the bottom of the den. In many of the smaller and curved 
bones, also, particularly in those of the lower jaw and toes, as well as in 
the curved teeth, (see Plate V. fig. 1 and 3 ) the convex surface only has 
been uniformly worn down and polished, whilst the ends and concave 
surface have suffered no kind of change or destruction (Plate V. fig. 
2 and 4): and this also admits of a similar explanation; for the cur¬ 
vature of the bone or tooth would allow it to rest steady under con¬ 
stant treading only in this position: as long as the concave surface was 
uppermost, pressure on either extremity would cause it to tilt over, 
and throw the convex side upwards; and this done, the next pressure 
would cause its two extremities to sink into any soft dirt on sub- 
