MAMMALIA. 61 



The Pliocene and Pleistocene mastodons just enumerated Pier-oases 



clearly possessed the ordinary elephant proboscis, and would m 38-42. 

 i_ ii 11 i -xt • t • n i Table-cases 



be elephants to all outward appearance. Young individuals, 23 24. 



however, exhibit a diminutive pair of tusks projecting from Stand B. 



the front of the lower jaw. They are thus reminiscent of 



their predecessors of the Miocene period in Europe and 



northern Africa, which had well-developed and functional 



lower tusks throughout life. These ancestral mastodons, of 



the genus Tetrabelodon, are illustrated by numerous remains 



from the Middle and Upper Miocene and Lower Pliocene of 



Pig. 54. — Skeleton of Mastodon americanus, from the Pleistocene of 

 Benton County, 'Missouri, U.S.A. ; greatly reduced. (Stand B.)! 



Europe in Pier-case 41 (42). None of the species were so 

 large as those of the genus Mastodon itself. Their skull 

 (Fig. 60) is quite like that of an elephant, and the spreading 

 upper tusks only differ from modern elephant tusks in being 

 provided with a band of enamel along one side. Their 

 lower jaw, however, is produced at the chin (symphysis) into 

 a remarkable bony spout-shaped elongation, tipped with a 

 pair of chisel-shaped tusks, which cannot have worked against 

 the upper tusks, but evidently met some kind of pad on the 

 palate. Tetrabelodon must thus have possessed an immensely 



