254 



SUBUNGULATA 



ORDER IX 



the series from Moerithermm to Eleplms. The gradual development of the 

 proboscis and tusks brings about a shortening of the maxillary and upward 

 displacement of the nostrils ; and this deformation accounts for the high 

 arch of the skull, the formation of air cells and the broadening of the pai'ietal 

 region. The premaxillaries overlap the maxillaries and form large cylindrical 

 sockets for the tusks. The upper jaw becomes deeper and the zygomatic 

 arch weaker. On the other hand, the symphysis of the lower jaw becomes 

 longer, but later on contracts after the lower tusks have been lost. The 

 ascending ramus of the lower jaw becomes higher, but at the same time more 

 slender, and the condyle gradually becomes more elevated. 



The extremities of the Prohoscidea (Fig. 336) are long and pillar-like, 

 and the long bones without marrow cavities. There is no clavicle. The 



ulna is distally much thicker than the radius. 

 The carpals are more or less serially arranged. 

 A centrale is present in the young elephant. 

 The lateral metacarpals (I and V) are shorter 

 and weaker than the in- 

 side ones. The whole 

 foot is encased in a single 

 covering, from which the 

 hoof-like nails of the toes 

 protrude only slightly. 

 The third trochanter of 

 the femur is usually lack- 

 ing. Tibia and fibula 

 are separated, the latter 

 distally thickened. It 

 articulates with the as- 

 tragalus and calcaneum. 

 The astragalus has a 

 slightly arched trochlea 

 and articulates distally 

 only with the navicular. 

 The Prohoscidea 



are 



Fig. 336. 



Right fore {A) and hind (B) foot of existing Indian elephant (ElepTias 

 indicits Linn.) a. Astragalus; c, cuneiform; c IL, c III., second and 

 third cuneiform; ca, calcaneum ; cb, cuboid ; /, lunar ; 7rt, magnum ; n, rootrictorl +n +Vio +rnvii/^Ql 

 navicular; R, radius ; sc, scaphoid ; W, trapezoid ; 17, ulna ; m, unciform. itJblllCLBU LU LUe uupioai 



portions of Africa and 

 Asia in recent times. They begin in the Eocene of Egypt, spread over the 

 Northern Hemisphere in the Miocene and reach South America only in 

 the Pleistocene. As index fossils their cheek teeth can be used only with 

 great circumspection, on account of the numerous transitional forms, all 

 closely allied to one another, and on account of the considerable variation 

 in size of the teeth of one and the same genus. 



3.1.3.3. 



Family 1. Moeritheriidae Andrews. 

 Second incisor above and below enlarged and the upper one 

 First incisor above and below, and P as well as 



2.0.3.3. 



developed into an arched tusk. 



the canine, small. Premolars simpler than the molars, and like these brachyodont. 



Upper premolars tritiibercidar, lower premolars composed of two anterior and one 



