THE EDENTATES 21 



In our collection, all from one point, there are thirty- 

 nine different species. Beside these Ameghino has de- 

 scribed a considerable number of species, some of which in 

 time will probably turn up at our locality; but others and 

 I think the majority will be found to be representative of 

 other localities which he worked. It is to be expected that 

 a difference of locality will make a little difference in the 

 fauna. Further I expect that no two localities represent 

 exactly the same period of time, though they may do so 

 approximately; but some of these local deposits must have 

 been begun earlier, and others probably lasted to a later 

 period. Thirty-nine species of mammals and land birds 

 is a fairly varied fauna for one spot; and the time element 

 involved in laying down the 50 feet which separated the 

 bottom from the top of the Deseado deposit is not probably 

 very long; for the material of which the deposit is com- 

 posed is of a character which would have been laid down 

 fairly rapidly. 



Of this fauna only 8 per cent belongs to the edentates; 

 and if any element were disproportionately represented it 

 would be this one, for the armadilloes have in addition to 

 the skeleton the hundreds of tiny plates of the carapace, 

 and several of the forms are represented by one or two 

 plates only. When compared with the condition in the 

 Santa Cruz this 8 per cent is strikingly small, for in that 

 later bed, fully 50 per cent of the finds represent edentates. 

 Are the Edentata just originating? Or, was the country 

 less favorable to their habitation? The edentates which 

 we did find are only slightly less advanced in their develop- 

 ment than those of the Santa Cruz. Also, though in- 

 frequent, all of the families of the Santa Cruz are repre- 

 sented. It would seem therefore that the origin of the 

 edentates was much earlier than the Deseado; and this 

 relative paucity of edentates is also characteristic of the 

 Casamayor and Astraponotus beds; but they are there, 

 and in considerable variety, though small numbers. It 



