EGYPTIAN TERTIARY VERTEBRATA 673 



teeth have comparatively low crowns, with two transverse 

 ridges. The humerus has all its ridges and processes for 

 the attachment of muscle greatly developed, indicating a fore 

 limb of great strength, and — judging from its form — possibly 

 employed in digging. The relationships of this creature are 

 unknown ; it is by some regarded as belonging to the Pro- 

 boscidea, and it has even been suggested that there may be 

 some relationship with the South American Pyrotheria. 



Although Arisinoitherium and Barytherium are interesting 

 for the peculiarities they present, their very isolation detracts 

 considerably from their importance, for they throw no light 

 on the earlier history of any of the previously known groups 

 of mammals. From this point of view the remains of primitive 

 Proboscideans from these Egyptian deposits are of vastly greater 

 interest, for they at once settle the point of origin of the groups, 

 and carry back the line to a generalised type of ungulate 

 showing only the beginning of the extraordinary specialisations 

 characteristic of the later forms. Previous to the discovery of 

 these Egyptian forms, the earliest Proboscideans known were 

 species of Tetrabclodon and Dinotherium from the lowest 

 Miocene beds of Europe, where they appear suddenly at this 

 horizon, no trace of any related form being found in the earlier 

 Tertiary deposits of that continent. The sudden appearance in 

 the European fauna of these and members of some other groups 

 led to a number of speculations as to where these animals had 

 originated. Osborn, Stephen, and Tullberg for various reasons 

 all came to the conclusion that the evidence pointed to the 

 existence of an Ethiopian land-area in early Tertiary times, and 

 they considered that not only the Proboscidea, but several other 

 groups — notably the Sirenia, Hyracoidea, certain Edentates, the 

 Antelopes and Giraffes, the Hippopotami, several divisions of 

 the Rodentia, and lastly the Anthropoidea — originated in that 

 region. Of many of these, the early forms have still to be 

 found ; but the predictions of the above writers have already 

 been fulfilled in the case of the Proboscidea, the Sirenia, and the 

 Hyracoidea, so that there is good reason to hope that ancestral 

 forms of some of the other groups will yet be discovered in 

 Northern Africa. 



The earliest Proboscidean yet known is Mceritherium, remains 

 of which are found in the Middle and Upper Eocene. This 

 animal was about the size of a Tapir, which, moreover, it must 



