ON THE PROBOSCIDEAN FOSSILS OF THE PLEISTOCENE DEPOSITS. 49 



identified. Specific determination of Mastodon is in no case ex- 

 pressed, but it is presumably M. americanus. The list men- 

 tions in all thirty-nine individuals of this genus. In ten cases 

 identification was made from other parts of the animals than 

 from their teeth, and it may, perhaps, be somewhat uncertain. 

 Twenty-one of these finds are reported as mammoths and five as 

 Elephas primigenius, making twenty-six specimens of this species. 

 Nineteen of these determinations were made from teeth, often oc- 

 curring with other bones, one appears to have been made from a 

 tusk, and four were probably made in absence of either teeth or 

 tusks. Elephas americanus is reported from two places in Iowa. 

 Ten of the specimens are spoken of merely as elephants, and these 

 are presumably Elephas primigenius. Except in two cases, the 

 determinations of these nine specimens were also made from teeth. 

 In one instance, only a tusk was present, and in another, both 

 teeth and tusks seem to have been wanting. In all, the list in- 

 cludes thirty-five elephants and thirty-four mastodons. Thirteen 

 specimens are reported merely as "proboscideans", as "mammoth 

 or mastodon", or as "elephant or mastodon". In eleven of these 

 cases, the remains did not include any teeth, and in nine there 

 were neither teeth nor tusks. Thus it appears that specific de- 

 terminations have not been made except in the presence of either 

 teeth or tusks. These furnish the most obvious and reliable char- 

 acteristics for that purpose. From the above facts, we may con- 

 clude that the determinations are sufBciently accurate to warrant 

 the general conclusion from the figures given that the remains of 

 the elephant and of the mastodon are about equally frequent in 

 these two states. It will be noticed that nearly all of the fossils 

 are from the drift-covered region. Professor J. D. Whitney* states 

 that in the lead region (the driftless area) mastodon remains are 

 much more frequent than those of the elephant. 



* Geological Survey of Illinois, Vol. I, p. 162. 



