474 LAND MAMMALS IN THE WESTERN HEMISPHERE 



which the females have a very small horn, or none at all, and 

 the males a large one. 



In the skeleton also (here were few differences, other than 

 those of size, between fAdinotherium and ^Nesodon; the for- 

 mer was not only smaller, but also lighter and more slender 

 proportionately, and there was no hump at the shoulders, 

 the spines of the dorsal and lumbar vertebrae all reaching the 

 same level, so that the back must have been nearly straight in 



Fig. 240. — \Adiaothcrium ovinum, snuill, horned ftoxodout of the Santa Cruz. Re- 

 stored from a skeleton in the museum of Princeton University. — Note the minute 

 horn on the forehead. 



the living animal. From the more general and constant pres- 

 ence of the frontal horn, \Adinotlierium was more probably 

 the ancestor of the horned ^Trigodon than was \Nesodon, but 

 until the intermediate forms shall have been recovered, no 

 definite decision can be made. 



The same or very nearly the same genera of the family 

 fToxodontidae lived in the Patagonian and Deseado stages,, 

 but there the record breaks off and can, for the present at least, 

 be followed no farther. It remains to be determined whether 



