138 TERTIAET VERTEBEATA OF THE FATtTM. 



succession. The differences between the palatines and pterygoids in the earlier and 

 later types are of course dependent on the same causes. 



The anterior portion of the skull, particularly the upper portion, is completely 

 wanting in the large specimen on which the above description is for the most part 

 founded; but another specimen (PL XIII.) supplies the necessary information 

 concerning this region. It is the anterior portion of a skull of a very young 

 individual in which the milk-teeth are still in use ; it includes the whole of the 

 frontals as far back as considerably behind the postorbital processes, the nasals, 

 premaxillaries, lachrymals, and most of the maxillae, including the zygomatic 

 process, also the palate as far back as the level of the middle of the zygoma. 

 There are two teeth, in situ on one side and three on the other ; they are probably 

 mm. 2, 3, 4, and will be described below. The crushed base of one of the milk- 

 tusks is preserved in the socket. As will be shown below, this specimen in the 

 shortening of the nasals and the shifting backwards of the narial opening supplies 

 a beautiful illustration of the approximation towards the later Proboscidean type found 

 in this genus. In the relations of the bones to one another it precisely resembles 

 Mephas. 



The right frontal (fr.) is mostly broken away, but the left is better preserved, and 

 although its actual junction with the parietal cannot be observed, nevertheless 

 little can be wanting from its hinder border. Together the upper part of the 

 combined frontals in the interorbital and part of the postorbital regions forms the 

 gently convex skull-roof. In this young specimen scarcely any trace of the supra- 

 temporal ridges (the divided sagittal crest) can be seen, but it is evident that they 

 ran on to the postorbital processes. External to these ridges in the postorbital 

 region the frontals run down into the temporal fossae, and are strongly convex from 

 above downwards. The postorbital processes are blunt prominences, from each 

 of which a ridge rnns downwards and backwards, separating the orbit from the 

 temporal fossa. Ventrally this ridge must have been continuous with that formed 

 by the free edge of the alisphenoid described above. In front of the postorbital 

 processes the frontals form a well-defined upper rim to the orbit, and anteriorly 

 they unite in suture with the maxillae, lachrymals, premaxillae, and nasals, their 

 general relationships to the neighbouring bones being exactly as in Elephas. 



The lachrymal [lac.) is a small bone wedged between the frontal and maxilla, 

 and grooved below by the upper surface of the antorbital canal. It is perforated 

 by a large foramen which lies within the border of the orbit ; above the foramen 

 and on the rim of the orbit there is a small but prominent tubercle. 



The nasals (na.) are short bones which already approximate very nearly in form to 

 those of Mephas. Together they project in a blunt point over the nasal aperture. 

 Posteriorly they are together roughly semicircular in outline and unite for the greater 

 part of their width with the frontals, but externally to these with the premaxilla;. 



