254: Barbour — Ligamentum Teres in Nebraska Proboscidea. 



belodon collected the past season by the writer. It shows 

 more striking peculiarities and is altogether more unique than 

 any longi rostral mastodon in our collections. Fortunately the 

 skull mandible and practically the complete skeleton were pro- 

 cured and will be the subject of a special paper. A little 

 farther west in Brown County the writer secured two longi- 

 rostral mastodons recently described as Tetrabelodon willis- 

 loni, from a lower horizon, and JEubelodon morrilli, from 

 a higher. The acetabula referred to Tetrabelodon willis- 

 toni are small, but half as large as mammoths. The cotyloid 

 notch is narrow and shallow, but the fossa is deep and 

 expanded toward the center of the cup, where it is rough and 

 pitted. In Eubelodon morrilli a perfect pelvis was found 

 with the skull and certain skeletal parts, so the identity 

 seems certain. The acetabula measure 6^ in. (165 mm ) across. 

 The fossae are 3 in. (T6 mm ) long by l| in. (3S mra ) broad. 

 They deepen centrally to a full inch (25 mm ) and are very 

 rough and pitted for ligamentous attachment. The corre- 

 sponding femur heads have pronounced scars. In this case 

 the existence of the round ligament seems reasonably certain. 

 It was presumably large and functional. Still further west in 

 Cherry County (in the Snake River beds, Pliocene) was found 

 the unique specimen, Tetrabelodon lulli. Its acetabula are 

 6|- in. (165 mm ) in diameter. The notches are narrow, and mod- 

 erately shallow, but toward the center of the cup the fossae 

 broaden, deepen to 1 in., and are roughly pitted. The corre- 

 sponding femur heads are scarred and pitted. From the 

 Pleistocene of the state come a number of acetabula and femur 

 heads of the later mastodons and mammoths. The acetabula 

 of Mastodon americanus average about 7 in. (I78 mm ) in diam- 

 eter. All show long broad, relatively shallow but well-devel- 

 oped fossae. Corresponding femur heads are smooth as in 

 mammoths and modern elephants. Our mammoths have large 

 acetabula measuring 8 to 8£ in. (203 to 216 mm ) across. The 

 femur heads are without scars. The fossae are 4 in. (101 mm ) 

 long, 2 in. (50 mm ) broad, and 1^ in. (32 ,um ) deep. The round 

 ligament was undoubtedly reduced but not suppressed. In 

 living elephants the acetabular fossae are filled flush with the 

 surface by osseous growth and absence of the ligamentum 

 teres is a character. A comparison of a number of specimens 

 seems to justify belief in the existence of the round ligament, 

 especially in our tetrabelodons. 



The accompanying figures are drawn from specimens in the 

 collections of Hon. Charles H. Morrill, in the Nebraska State 

 Museum. 



The University of Nebraska, 

 September 20, 1915. 



