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 
