No. 492] 



SOME AMERICAN CHALICOTHERES 



749 



The Pes. — In a general way the tarsus (No. 1710) in Moropus 

 is much like that of the Rhinocerotidae. There are, however, 

 many differences viz: the navicular is supported entirely by the 

 astragalus and the cuboid by the calcaneum as in ]Meniscotherium. 

 The trochlea of the astragalus is somewhat more deeply grooved, 

 the internal and external condyles are more even in size and the 

 external condyle is not interrupted as in Titanotlierium, but con- 

 tinues below the articular facet for the navicular. The pes is tri- 

 dactyl; there is no indication of lateral digits. The second meta- 

 tarsal is shorter and also somewhat lighter than the third and 

 fourth which are of equal size. The articulation for the proximal 

 phalanx is confined almost entirely to the dorsal face of the 

 bone, while on the plantar face are deep, broad grooves, which 

 are divided by heavy keels. The sesamoids are very heavy and in 

 some cases they are co-ossified, forming a broad open groove for 

 the tendons. As in the fore foot the claw-bearing ungulae are 

 deeply cleft, but of more nearly equal size. 



From the study of the foot and limb structure of Moropus it is 

 very evident that the animal was digitigrade. Professor Osborn 

 has called attention to the fact that the European forms were 



almost certainly sub-diuitiurade." ^ 



The remains above dcscrihcd i No. 1()04) belong to an individual 

 very nearly the size of Clialicofhcrliim goldfussi of Europe, or the 

 size of a small specimen of Titanotherium from the American 

 Oligocene. Smaller remains are more common in the quarry, 

 indicating two or more species, or a great range of individual 

 variation. This question will })e taken up in a later publication. 

 There are ])er]iaps twentv individuals of Moropus represented in 

 the collection of the (^anicoie Miisinun, which were secured in the 

 Agate Sprinu- Fossil (^iiarrv. 



In ChaUrnthrr-nnn ,,nhljussi Kaup. 1" l.a. ilu. inrcTnal face of 

 the ectol<>i>h W-.l.ai.cd and the intrnial tiil.r.vlr ,,f a dillnvnt form 



