MAMMOTHS AM) MASTODUXS 



jaw is ralluM" short, and the lower tusks and tlicir sockets tiinie<l down at a 

 sliarp allele lo the j)hine of the '•riiKhii*; teeth. It is a rare form, and th<' 

 only representatives that we have found are from llie IMiocene of Texas 

 and l*leistoeene of Mexico. 



The Primitive Four-tusked Mastodons. (lenus Trilophodon (= 

 Gonipliothcriutn). This grouj) includes a large mnnher of species from tlie 

 Miocene of Europe, Asia, Africji and North America, representing the 

 ancestral stock of the various hiter types of mastodons and ])r()l)al)ly of 

 ek^phants. The typical form is T. anijustidens Cuvier of Europe, a species 

 with exceptionally long lower jaws and tusks. In this country it is admir- 



After Oifborn 



Fig. 7. Skull of Primitive Mastodon, Trilophodon productus from 

 Miocene of Texas. One-tenth natural size. 



ably represented by T. productus Cope. The upper tusks are straight or 

 slightly down-curved, the lower tusks well-developed, and both carry a strip 

 of enamel. Two or three grinders are normally in use at once, and the 

 second true molars have three cross crests. In one group (Bunolophodon) 

 the cross crests are strongly tref oiled; in another (Zygolophodon) they are 

 more ridged, the valleys less obstructed, approaching the American Mas- 

 todon in type. Different species in the first group approach more or less 

 to Dihelodon, Tetralophodon and Rhyncotherium in the characters of the 

 grinding teeth. 



Although chiefly from the Miocene, there are several imperfectly 

 known Pliocene or even Pleistocene species referred to it. These represent 



