294 Bulletin American Museum of Natural History. [Vol. XVI, 



Length of diastema 20 mm. 



" " three upper molars (?p*-m^) 15 



" " enlarged " molar (? p*) 8 



Width of " " " " 6.5 



Height of same (root and crown) 12 



Estimated length of lower jaw 58 



Depth of jaw beneath molars 15 



Height " " (angle to tip of coronoid process) 41 



Length of enlarged lower molar (? P4) 10 



Width of " " " " 5.5 



This remarkable skull has no parallel among the Rodentia. 

 Haplodontia most nearly approaches it in width, but the horn- 

 cores and the specialized teeth are unique. 



HIND LIMB AND FEET OF MYLAGAULID^. 



We know but little as yet of the skeleton of this family. 

 The pelvis was very massive, and beaver-like on a smaller 

 scale, the tail probably not flattened, and the scaphoid and 

 lunar were united. A metacarpal associated with two teeth 

 of Mylagaiilus shows some remarkable characters. It is 

 nearly as large as the metacarpals of Castor canadensis and 

 much stouter. The distal facet is strongly keeled on the 

 inferior surface, in a manner recalling the distal ends of meta- 

 podials of Chalicotherium or metacarpals of Dasypus. The 

 facet is limited superiorly, so that it is not at all refiexed over 

 the superior surface of the metacarpal, but faces entirely in- 

 feriorly and distally. The characters of the bone may be 

 taken to indicate the presence of large digging claws on the 

 manus. 



I refer also to this family a remarkable specimen in the Cope 

 Collection from the Loup Fork beds of the Republican River, 

 Nebraska, consisting of a nearly complete hind limb and foot, 

 with an ungual phalanx of the fore foot, not associated with 

 any parts of the skull. This specimen combines characters of 

 a Castoromorph rodent, with a resemblance to the modern ar- 

 madillo so striking that I am unable to state positively that it 

 is not edentate.^ As nearly as I can judge, however, the ar- 



' Professor W. B. Scott, whose recent extensive and thorough studies of the Santa 

 Cruzian fauna give especial weight to his authority, has examined this specimen and 

 pronounces it probably rodent and certainly not edentate. 



