312 ON THE EXTINCT MAMMALIA OF 



Lines. 



Length of the crown at the median buttress, . . . . 5J 



Length of the antero-external lobe, . . . . . . 7h 



Antero-posterior diameter externally, . . . . .14 



Transverse diameter, . . . . . . .13 



ANCHIPPUS. 



The distinctive characters of this genus, as determined from a fragment of a supe- 

 rior molar tooth, are as follow : The median lobes are better developed than in the 

 former two genera, and the internal lobes are in a proportionate degree diminished. 

 The postero-median lobe in its course gives oil" a process, which approaches, without 

 reaching, the inner extremity of the median lobe in advance. Likewise the posterior 

 crescentoid tubercle of the crown gives off a process, which approaches the inner ex- 

 tremity of the neighboring median lobe, but stops short and connects itself with the 

 contiguous internal lobe. In other words, the median lobes and posterior tubercle, 

 with their offsets, exhibit a tendency to conjoin, and thus form a pair of crescentoid 

 lobes embracing the external ones, as do the corresponding columns in the Equidce. 



Anchippus Texanus. 



Dr. B. F. Shumard submitted to my examination the greater part of an upper 

 molar tooth of an animal, apparently allied to Anchitlierium, from Washington Co., 

 Texas. The specimen was obtained from " Hutchin's Well," fifty feet below the 

 surface, from a yellow sandstone, supposed to be of miocene age. 



The tooth, represented in figure 13, plate XXI, has lost the outer portion of the 

 external lobes, but is otherwise sufficiently perfect to exhibit its peculiar characters. 

 Its size is nearly the same as in the teeth of Anchitlierium aurelianense, with which it 

 also agrees in general proportions and construction. 



' Six pairs of lobes compose the crown, holding the same relative position with one 

 another as in Anchitlierium ; but they, and the intervening valleys, appear propor- 

 tionately somewhat deeper. 



The external lobes appear to have had the same form as in Anchiiherium. The 

 internal lobes also have the same form, but are longer and less robust, while the 

 median lobes are proportionately more robust, or, in other words, the internal and 

 median lobes approach nearer to equality than in Anchitherium. The postero-median 

 lobe pursues the same course as in the latter genus, and outwardly joins the external 

 lobes at their angle of conjunction. From near the middle of its course it gives ofi' a 

 process, which is directed towards the inner thicker portion of the antero-median 

 lobe, but ceases a short distance from it. The pi'ocess approaches the antero-median 



