EXTRAORDINARY PROFUSION OF HIPPOPOTAMI 51 



fangs. This breccia has been classed with the breccia 

 of ordinary bone-caves, the former resort of pre- 

 daceous animals, but the bones are not gnaived, as is 

 the case with the bones in those caves, and besides 

 they are the bones almost exclusively of Hippopotami , 

 of which the remains are very rare in caves, as the 

 weight of the animal must usually have led to its 

 being devoured on the spot where it died. The only 

 other suggestion that has been made is that the bones 

 are those of successive generations of Hipp^^ ^cami 

 which went there to die. But this is not the habit 

 of the animal, and besides, the bones are those of 

 animals of all ages down to the fcetus, nor do they 

 show traces of weathering or exposure. 



The explanation which suggests itself to me is 

 founded on the local topographical features of the 

 island. The plain of Palermo is encircled by an amphi- 

 theatre of hills, rising to the height of 2,000 to 3,000 

 feet, and presenting mural precipices towards the 

 plain. The caves are situated near the base of this 

 escarpment, and at San Giro the breccia not only sub- 

 tends the cave, but extends to some distance on the 

 slope in front as well as on either side. My supposi- 

 tion is, therefore, that when the island was submerged, 

 the animals in the plain of Palermo naturally retreated, 

 as the waters advanced, deeper into the amphitheatre 

 of hills until they found themselves embayed, as in 

 a seine, with promontories running out to sea on 

 either side, and a mural precipice in front. As the 

 area became more and more circumscribed the animals 

 must have thronged together in vast multitudes, 



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