FOSSILS IN THE BEACH AT CORRIGUEN AIKE. 73 



imbedded bore evidence of having been deposited over the flood plain of 

 some stream or shallow lake. On walking about over the surface at low 

 tide, there could be seen the skulls and skeletons of those prehistoric 

 beasts protruding from the rock in varying degrees of preservation. At 

 one point the skull and skeleton of Nesodon would appear, at another 

 might be seen the limbs or perhaps the teeth of the giant Astrapothfrium 

 just protruding from the rock, while a little farther on a skull and jaws of 

 the little Icochilus grinned curiously, as though delighted with the pros- 

 pect of being thus awakened from its long and uneventful sleep. On one 

 hand, the muzzle of a skull of one of the larger carnivorous marsupials 

 looked forth, with jaws fully extended and glistening teeth, the charac- 

 teristic snarl of the living animal still clearly indicated, while at frequent 

 intervals the carapace of a Glyptodon raised its highly sculptured shell, like 

 a rounded dome set with miniature rosettes, just above the surface of the 

 sandstones. Throughout eighteen years spent almost constantly in col- 

 lecting fossil vertebrates, during which time I have visited most of the 

 more important localities of the western hemisphere, I have never seen 

 anything to approach this locality near Corriguen Aike in the wealth of 

 genera, species and individuals. The bones of these animals were not the 

 only records preserved of their former existence, for at certain places, on 

 looking across the surface of the sandstone, one could see their fossil foot- 

 prints. At one locality especially favorable, where the erosion had 

 evidently taken place along a single bedding plane over a considerable 

 area, a series of tracks was seen extending uninterruptedly fora distance of 

 about one hundred feet, making it quite possible to determine the exact 

 stride of the animal. The presence of these tracks is conclusive evidence 

 that these animals roamed over, lived and died in this very region during 

 the time when the sandstones and shales which contain them were being 

 deposited, and precludes the possibility of the deposits having been laid 

 down over the bottom of a great lake, or any other large and stable body 

 of water. The origin of these deposits will be fully discussed when we 

 come to treat of the geology of the region. 



As will readily appear from the preceding remarks, our work of collect- 

 ing fossils was restricted each day to the period of low tide. The principal 

 fossil-bearing locality was limited to an area about one and a half miles 

 in length, with an average breadth of perhaps three hundred yards. As 

 the water gradually disappeared each day from this area with the receding 



