E. II. Barbour — New Longirostral Mastodon. 523 



Fig. 1. 



For this new proboscidean, we wish to propose the name 

 Tetrabelodon osborni, in recognition of Dr. Henry Fairfield 

 Osborn. The peculiarities of the 

 skull promise to be so great that 

 eventually this specimen must be 

 assigned to a new genus. 



In this Tetrabelodon a unique 

 adaptation presents itself, and a new 

 principle seems to be involved, 

 namely, the use of the mandible and 

 the mandibular tusks for work and 

 defense. There is a suggestion in 

 the protruding mandible and its 

 strong, recurved tusks, that they 

 may have functioned as a sort of 

 shovel in digging and tearing up 

 roots, aquatic plants, and the like. 

 However this may be, the inferior 

 tusks are well developed and modi- 

 fied, while the superior, though heavy, 

 are short and seemingly useless. 



The mandible of Tetrabelodon 

 osborni seems to differ in many 

 essentials from other longirostral 

 forms found in the State. Such 

 differences can scarcely be attributed 

 to age, sex, or individual variation, 

 and must be counted specific. The 

 mandible is long and very strong, 

 the rami widely divergent, the angle 

 thin and reflected, the symphysial 

 portion relatively short, noticeably 

 broadened and somewhat upturned 

 at the tip. The lingual groove is 

 moderately deep behind but shallow 

 in front, and the walls converge 

 from 5 inches posteriorly to 3 inches 

 anteriorly and blend at once into 

 the flattened, broadened tip. The 

 ascending ramus is very oblique, the 

 condyle large, the coronoid low, 

 and the sigmoid notch shallow and 

 straight. The length and leverage 

 of this great jaw seems to call for 

 broad, erect, ascending rami. Just 

 back of the molars the jaw is thin, 

 in front very thick. Anteriorly, the 



