DAKOTA AND NEBRASKA. 



321 



viewed as indicating a new species, and was described in the Proceedings of the 

 Academy for 1854, page 90, under the name oi Ilippodoii speciosus. The specimens 

 of the former figures look so much like the latter as to render it probable that they 

 belonged to the same animal. 



16. A fragment of the left side of the lower jaw, containing the supposed third 

 molar. This is inserted by fangs, and its triturating surface is represented in 

 figure 24. The breadth of the surface is ten and a half lines ; its thickness, inde- 

 pendent of the cementum, six lines. 



17. Three isolated molars, represented in figures 25 — 27. The specimen of figure 

 25 is a first temporary tooth of the left side. The others held an intermediate posi- 

 tion in the permanent series; that of figure 26 is nearly half worn away; that of 

 figure 27 is comparatively but little worn. These display a peculiar arrangement of 

 the enamel on the triturating surface, quite different from that of any of the teeth 

 previously mentioned, but they are sufficiently alike among themselves to render it 

 probable that they belong to the same species . 



18. A series of the anterior three molars, apparently belonging together. Their 

 triturating surfaces are represented in figure 28, and approach in character those of 

 the last mentioned specimens as to render it probable that they belonged to the same 

 species. The specimen of figure 27 probably held the same relationship of a fourth 

 tooth to this series, and that of figure 26 probably is a fifth molar. 



The measurements of the three teeth are as follow : 



Lines. 



. 32 



Space occupied by the three molars, 

 Breadth of first molar. 

 Length externally at middle, 

 Breadth of second molar, 

 Length of do.. 

 Breadth of third molar, 

 Length of do., 



This series of teeth bears such a near resemblance in general ap 

 age, and proportionate size, to the back series represented in figure 11, that, were it 

 not for the striking difference in the arrangement of the enamel on the triturating 

 surface, I should have referred them to the same individual. 



19. A lower molar, probably the second or third of the left side, represented in 

 figure 29. It is much worn, and apparently belonged to a larger animal than" any of 

 the preceding specimens. It accompanied the upper molars of Hlpparim occideniale, 

 from White River, represented in figures 1—5, plate XVIII, and was, when first seen, 



41 



. lOi 



. 12J 



. lOi 



. 17 



. lOi 



. 20i 



pearance, relative 



