250 



also resembles the corresponding toolli of Fii^f. 6, Plate XXVII, of the Ex- 

 tinct Mammalian Fauna of Dakota, &c., sufficiently to pertain to the same 

 species. This specimen was obtained on Little White River, Dakota, and 

 was referred to Protohiiipus placidus. The proportions of the former are the 

 same, but, being more worn, it is shorter, and appears larger at the triturating 

 surface. At the same stage of abrasion they would even bear a greater 

 resemblance to each other, as the open fold on the posterior part of the Little 

 White River specimen, in a more worn condition, would then form an islet on 

 the triturating surface, as in the Texas specimen. 



The measurements of the specimen, in comparison witii those of the Little 

 White River specimen, are as follows: 



Texas 

 specimen. 



Dakota 

 specimen. 



Length of crown at tbe antero-internal column.. 

 Length of crown at the postero-external cohiinn . 



Breadth of crown at the triturating surface 



Width of crown at the triturating surface 



Lines. 



6 

 10 



H 



7 



Lines. 

 S 



9 



S 



The Museum of the Smithsonian Institution contains several specimens of 

 teeth apparently of ProtoMppus perdilus and Meryckippus mirabUis, obtained 

 by Mr. Clarence King in Utah. 



AXCHITHERIUM. 



AnCHITHERIUM (?) AUSTRALE. 



Among the Texan collection of fossils there is a specimen of peculiar 

 character rejn-esented in Fig. 19, Plate XX. It was tbund in association with 

 that of Fig. 16, of the same plate, in Washington County, Texas. It is the 

 first of the series of six large upper molars as existing in equine animals, but 

 exhibits in front the impress of a premolar larger than usual in members of 

 the order. The specimen is broken at its outer part, but the remainder 

 is nearly as characteristic as if the whole were complete. The crown is so 

 worn away that the dentine is continuous upon all the constituent lobes. An 

 olilique valley extends from the inner side and ends in a foot-like expansion 

 near the center of the triturating surface, and l)ack of the center there re- 

 mains a crescentic enamel lake. 



