PAL^OMASTODON. 139 



The premawillce (pmx.) send up a long tongue of bone along the sides of the nasal 

 opening, thus completely shutting out the maxillae from any share in its border. 

 Anteriorly they are prolonged forwards, forming a projecting snout, on either side 

 of which are the alveoli of the large incisor tusks, which must have projected 

 forwards and somewhat downwards. Here the only trace of teeth is a portion of 

 the crushed base of one of the tusks (i.), probably of the milk-series ; this tooth seems 

 to have been enamel-clad on the outer side only. On the palate the premaxillse 

 seem to have appeared to a very sniall extent only, but the precise division 

 between them and the maxillae cannot be made out. The upper surface of the 

 conjoined bones is slightly concave from side to side, the first indication of the 

 form so characteristic of the later Proboscidea. Posteriorly their median suture 

 opens for a short distance in a sort of cleft (Ifor the mesethmoid cartilage), on 

 either side of which they are perforated by a small foramen. The floor of the nasal 

 cavity is much more in the same straight line with the upper surface of the anterior 

 part of the premaxillae than in Mephas, and the premaxillary portion of the snout, 

 as a whole, is relatively much longer and narrower. The nasal opening {nar.), looked at 

 from the front, is quadrate in outline ; its upper posterior angle lies considerably in 

 front of the orbit and only a little behind the level of the facial opening of the 

 antorbital foramen. In Mephas, on the other hand, the great difference is that 

 the nasal opening is largely behind the anterior border of the orbit, and the whole 

 facial region is much shortened up. 



The maxiUce [mx.) are not completely preserved posteriorly. In front the facial 

 portion extends up the side of the face to the level of the top of the nasal opening, 

 and helps to form the anterior border of the orbit. The base of the zygomatic 

 process is perforated by a large antorbital canal, which opens on the face by 

 two foramina (a.o.f.) — the upper small, the lower much larger. The process itself is 

 stout ; it forms the lower border of the orbit, but posteriorly the postorbital process 

 is actually formed by the anterior end of the overlapping jugal (Ju.) above described. 

 The palate is fairly broad and is slightly arched ; it narrows in front, where the 

 maxillse seem to" run forwards beneath the premaxillae as in other Proboscideans. 



A restoration of the whole skull founded upon the two specimens above 

 described is given in text-fig. 48 (p. 131). 



Upper Dentition (PI. XII. figs. 1, 1a; PI. XIV. fig. 2). — In the upper jaw there 

 are seven teeth on each side : viz., an incisor (i. 2), three premolars, and three molars. 

 The first molar is always much smaller than the others. 



The incisor is a large, laterally compressed, downwardly directed tusk, sometimes 

 with a slight spiral twist; the anterior edge is rounded, the posterior sharper. 

 There is a broad band of enamel on the outer face. One nearly complete 

 specimen measures 25'3 cm. long in a straight line. Behind the tusk there is a 

 diastema of at least 9-10 cm. 



t2 



