MCERITHEEIUM. 103 



distance ; but towards their anterior end they again diverge, and the sagittal crest also 

 divides into the feebly marked supratemporal ridges, which are continued forwards on 

 the frontals, terminating in the neighbourhood of the orbits. Ventrally the parietals 

 unite behind with the squamosals and probably with the alisphenoid ; farther forwards 

 with the frontals, which they overlap anteriorly to a considerable extent in a sort of 

 squamous suture. 



The frontals (fr.) are large bones which meet .in the middle line, forming the flat 

 roof of the skull between the obscure supratemporal ridges, which terminate over 

 the small orbits, though there are no distinct postorbital processes. Anteriorly the 

 frontals are separated by the nasals, which run back for some distance between them ; 

 they end in front in a rounded point about on a level with the anterior border of the 

 orbits, and are separated from the premaxillse by a short interval, owing to the fact 

 that the nasal sends down a process which joins the maxilla. The lachrymal cannot 

 be made out in any specimen examined, this region being usually very badly preserved. 

 In one case there is on the edge of the orbit a small tubercle presumably borne on 

 the lachrymal, but there is no evidence of a lachrymal foramen. 



The nasals (na.) are fairly large bones, which run back some distance between the 

 frontals. As they pass forwards they widen out, till at their widest point they form 

 a short suture with the maxillae. In front of this they again narrow between the 

 upper ends of the premaxillse. Anteriorly they terminate in bluntly rounded ends, 

 which slightly (about 7 mm.) overhang the anterior narial opening. The difference 

 between this region of the skull in Palceomastodon and Moeritherium seems to be due 

 to the shifting back of the nares (consequent on the development of the proboscis) in 

 the former, which leads to the reduction of the nasals and the carrying back of the 

 facial processes of the premaxillse till their upper ends meet the frontals and exclude 

 the nasals from contact with the maxillae. 



The premaxilloB {pmx.), which together form the broad blunt snout, are chiefly 

 remarkable for the depth and solidity of their alveolar region, resulting from the 

 great enlargement of the tusk-Uke second incisors. The chief consequence of this 

 modification is, that the floor of the narial cavity is raised much higher above the level 

 of the alveolar border than usual, and the distance between it and the palate is 

 greater. In the skull figured in PI. VIII., a portion of the anterior region of these 

 bones overlying the median pair of incisors is broken away, but in another specimen 

 the upper surface of this anterior region is seen to be deeply grooved in the middle 

 line, the depth of the groove being increased by the presence of prominent ridges on 

 either side of it ; outside these again, and separated from them by slight depressions, 

 are the prominences formed by the large alveoli of i. 2. The upper surface of the 

 bones forms the floor of the nasal cavity, which, owing to the shortness of the nasals, 

 is exposed for some distance. The presence of the ridges and grooves on the front of 

 the snout may indicate that there was a mobile upper lip or short proboscis requiring 



