0. a Marsh— Principal Characters of the Tillodoniia. 251 



The two anterior upper incisors are large and scalpriform, 

 and faced in front with enamel. They grew from persistent 

 pulps, and strongly resemble the corresponding teeth in Eodents. 

 (Plate IX, figure 1.) The upper canines were quite small, and 

 separated by a diastema from the first premoJar. In the upper 

 true molars, the fore and aft diameter is much less than the 

 transverse, and the crowns are very short. The form of these 

 teeth is well shown in Plate IX, figure 4, which repj-esents a 

 nearly unworn last upper molar, natural size. 



The lower jaw in Tillotherium is elongate and massive, and 

 the symphysis is completely ossified. The condyle is broad, 

 convex transversely, and raised above the line of the teeth. 

 The coronoid process is stout, and of moderate height. The 

 angle is thin, and not inflected. The anterior incisors are large 

 and scalpriform, and faced in front with enamel. The canine 

 ijuite small. The lower molar series is of the Palceotherium 

 and the last lower molar has a well developed third lobe, 

 le vertebrae of Tillotherium resemble those of some car- 

 nivores. The cervicals are short, and the ends of the centra 

 nearly flat. The dorsals are of moderate length, and also 

 amphiplatyan. The lumbars are quite large. The humerus is 

 stout, and broad transversely at the distal end, which has a 

 supra-condylar foramen. The radius and ulna are separate, 

 and of nearly equal size. The radius is short, and both ends 

 are expanded transversely, indicating but little rotation. The 

 scaphoid and lunar bones are distinct,* and the pisiform is 

 large and stout. The feet were plantigrade. There were five 

 digits in the manus, the first being well developed. The meta- 

 carpals are short, and the terminal phalanges long, compressed 

 and pointed, somewhat similar to those in the Bears. (Plate 

 IX, figure 3.) The femur is of moderate length, and its head 

 has a pit for the round ligament There is a well marked third 

 trochanter. The distal end of the femur is compressed in a 

 fore and aft direction. The tibia and fibula are distinct, and 

 the latter is curved and slender. The calcaneum is elongate, 

 and the astragalus, depressed, with only a slight superior 

 groove. The hind feet were plantigrade, and the five digits 

 were similar to those of the manus. 



The remains of this genus at present known are from the 

 Eocene of Wyoming. The specimens preserved indicate ani- 

 mals from one-half to two-thirds the size of a tapir. 



Yale CoUege, New Haven, Feb. 18, 1876. 



* The scaphoid and lunar bones have not yet been found united in any Eocene 



type, 



The 



