MARYLAND GEOLOGICAL SURVEY 151 



As time passed the elephants increased greatly in size, the skull and 

 jaws became comparatively much shortened, the teeth larger, fewer in 

 number and with more complicated enamel folds, the trunk became 

 longer, the lower tusks disappeared and the upper tusks increased greatly 

 in length and curvature. 



The accompanying map shows the distribution of true elephants in 

 North America and may be regarded as rather conservative. It is entirely 

 probable that future discoveries will considerably extend the boundaries 

 here assigned to the various species. On the other hand, it is to be un- 

 derstood that specimens have not been found throughout the entire re- 

 gion covered by the map, but that the range has been extended in places 

 by bridging over gaps where it is entirely probable specimens will yet be 

 discovered. 



The map is based largely on specimens in the U. S. National Museum 

 which were kindly furnished by Mr. Eichard Eathbun, and com- 

 prise teeth from very many and widely separated localities. These have 

 been supplemented by material in the American Museum of Natural His- 

 tory and by the collections of the Maryland Geological Survey. It will 

 be noted that there is a gap in the distribution of the mammoth in 

 Alaska, and this, as stated by George M. Dawson, corresponds with a 

 large glaciated area. Of course, the mammoth crossed, or went around 

 this in some way, just where we shall undoubtedly know some time when 

 this region shall have been more thoroughly studied by geologists. 



Some of the occurrences of Eleplias seem to be entirely accidental, 

 among these the tooth on Long Island in the eastern part of Hudson 

 Bay, and on the Pribilof Islands are instances. In both cases it is quite 

 probable fhat carcasses or portions of carcasses were carried thither by 

 water or ice. 13 The occurrence of the Pribilof specimens has been used 

 as an argument to show that these islands and the adjacent marine 

 plateau were above the sea when the mammoth crossed into North 

 America, but while this seems entirely correct as far as the elevation of 

 the land is concerned, it is believed that the remains were carried to the 



33 This applies particularly to the Hudson Bay specimen which lies far from 

 any other recorded occurrence of mammoth remains. 



