BIG BADLANDS OF SOUTH DAKOTA. 



69 



There are comparatively few specimens available of this species. 

 Additional ones would undoubtedly afford a larger series of size vari- 

 ants and close some of the gaps, but even those listed above are suffi- 

 cient to show intergradations by less than ten per cent, in some cases 



/z6QJ,x^/^. 



12662, X 3/4 



Fig. 2. A, maximum, B, intermediate and C, minimum size variants of 

 Hyracodon nebrascensis. Upper premolar-molar series of the left side in 

 crown view, three fourths the natural size. Specimens No. 12563, 12687, 

 12662 Princeton University Geological Museum. 



^ Measurements given by Cope in type description. 



® Measurements given by Troxell, loc. cit., p. 40. 



" Scaled from Lambe's " natural size " figure, loc. cit, Plate I. His table 

 of measurements in the text (p. 40) gives 62 mm. for this dimension, li this 

 is correct, there are intergradations of less than 10 per cent, throughout in 

 the variation series listed above. 



