MUSEUM OF COMPAKATIVE ZOOLOGY. 155 



skeleton of this species ; it is relatively lighter and more slender than in the 

 larger species, but otherwise not different from it. Most important is a speci- 

 men containing all the metacarpals and phalanges in undisturbed position, and 

 this shows most distinctly the presence of the pollex, as one of us* had pre- 

 viously shown to be true in the case of 0. Culbertsoni. This correspondence 

 between the two species removes all suspicion that the pollex in the specimen 

 first described might be a case of abnormal polydactylism. The discovery of 

 a five-toed artiodactyl is of the utmost importance, as it furnishes the demon- 

 stration of what has long been surmised, that the ungulates of both odd and 

 even-toed series have been derived from pentadactyl forms. 



Eucrotaphus (Oreodon) major, Leidy (Eporeodon major, Marsh). This 

 genus differs from Oreodon in the presence of large inflated tympanic bullae, and 

 also {fide Marsh t) in the absence of a pollex. The dentition and char?cter of 

 the skull are identical in the two genera. 



Agriochoerus latifrons, Leidy. Isolated jaws and teeth. 



SUID^. 



Hyotherium (?) americanum, sp. nov. There is in the Princeton Museum 

 a suilline skull from the White River formation, which cannot be corre- 

 lated with any of Dr. Leidy's genera. It agrees very closely and is probably 

 identical with the Hyotherium of Europe, and will be provisionally referred to 

 that genus. In the Cambridge collection there is a suilline hind foot, which 

 may be referred to the same species. The astragalus is very oblique, the 

 external condyle greatly exceeding the internal in size ; the neck is short and 

 the distal end broad ; the calcaneal facets are confluent. The cuboid is low, 

 broad, and deep (antero-posteriorly). The metatarsals are very suilline in 

 character, the median pair short and massive, the laterals shorter and espe- 

 cially more slender ; the proximal ends are all on the same transverse line, and 

 the articular faces nearly plane ; the trochlear ridges on the distal ends are 

 confined to the posterior aspect, thus differing from Sus, Dicohjles, and other 

 recent genera. The phalanges of the median digits are heavier but not much 

 longer than those of the lateral digits. 



Measurements. 



M. 



Astragalus, length (outer side) 032 



" width trochlea 019 



Cuboid, length 016 



width 015 



Metatarsal II., length 048 



III. " 063 



* Scott, Proc. Am. Ass. Adv. Sci., 1884, p. 493. 

 t Dinocerata, p. 187, fig. 162. 



