"XI PHENOMENA OF ORGANIC NATURE 351 
have entirely perished, and left no trace whatever 
_ of their forms, may be proved to you by other 
considerations. There are large tracts of sand- 
stone in various parts of the world, in which 
nobody has yet found anything but footsteps. 
Not a bone of any description, but an enormous 
number of traces of footsteps. There is no 
question about them. There is a whole valley in 
Connecticut covered with these footsteps, and not 
a single fragment of the animals which made 
them have yet been found. Let me mention 
another case while upon that matter, which is 
even more surprising than those to which I have 
yet referred. There is a limestone formation near 
_ Oxford, at a place called Stonesfield, which has 
yielded the remains of certain very interesting 
mammalian animals, and up to this time, if I 
recollect rightly, there have been found seven 
_ specimens of its lower jaws, and not a bit of any- 
thing else, neither limb-bones nor skull, nor any 
part whatever; not a fragment of the whole 
system! Of course, it would be preposterous to 
imagine that the beasts had nothing else but a 
lower jaw! The probability is, as Dr. Buckland 
‘showed, as the result of his observations on dead 
_ dogs in the river Thames, that the lower jaw, not 
_ being secured by very firm ligaments to the bones 
of the head, and being a weighty affair, would 
easily be knocked off, or might drop away from 
_ the body as it floated in water in a state of de- 
