104 



I>k\ ('. W. ANDliKWS ON TIIK 



for fche great muscles necessary to support the heavy head. The reduction of the 

 nasal hones and the posterior position of the external nares is due to the presence of 

 the proboBoiSj which also accounts tor the width and concavity of the premaxilhe 

 hetween the sockets of the tusks. The depth of the alveolar region of the maxillae is 

 due to the large size and peculiar mode of succession of the molars. 



There is no post -glenoid process, l»ut a broad post -tympanic process of the squamosal 

 meets the hinder border of the glenoid surface and forms the boundary of the external 

 auditory meatus. The jugal is small and forms only the middle of the jugal arch, 

 though it sends back a prolongation beneath the zygomatic process of the squamosal as 

 far as the glenoid surface. There is no condylar foramen. 



The Mandible (tigs. 2 and 3). —The horizontal ramus is very massive owing to the 

 great size of the molar teeth. The symphysis] region is short and spout-like, and is 

 prolonged downwards into a short blunt process, the last remnant of the immensely 

 prolonged symphysis found in the form next to be described. The ascending ramus 



Fig. 4. — Skull of Mastodon americanus, Cuvier. Pleistocene. N. America. 



slopes somewhat forwards and terminates in a rounded articulation ; the coronoid is 

 short and does not rise as high as the articulation, and its anterior border arises on 

 the outer surface of the jaw in front of the hinder extremity of the molar series. 

 The teeth of Elephas are so well known, that any detailed description of them 

 is unnecessary, except so far as is needful for comparison with the earlier types. 



There is a large pair of tusk-like upper incisors (I. 2) which are homologous with the 

 second pair of the full mammalian dentition ; the dentine presents the peculiar 

 "engine-turning" characteristic of elephant ivory ; there is a small enamel cap lost 

 through wear at an early age. The permanent incisors are preceded by a pair of milk 

 teeth shed very soon. There are during the animal's whole life six pairs of cheek 

 teeth in the upper jaw, of which the anterior three are milk-molars, never replaced by 

 premolars. The succession of teeth is from behind, the whole series moving slowly 

 forwards and the anterior worn teeth being shed as the hinder ones come into position, 

 and the true molars are so large that never more than portions of two on either side are 



