THE AFTONIAN HOKSES 



345 



measurements of the teeth of the domestic species, expressed in milli- 

 meters, as given by Gidley in the table on page 98 of volume xiv of the 

 Bulletin of the American Museum of Natural History. Only the trans- 

 verse diameters are compared, but the other dimensions show correspond- 

 ing differences in size. In the case of the teeth of the Gladwin horse, to 

 quote from Gidley, "the transverse diameters were measured across from 

 the exterior ridge of the mesostyle to the exterior wall of the posterior 

 lobe of the protocone, exclusive of cement." In the Gladwin horse fully 

 half the original length of the teeth has been worn away. The antero- 

 posterior dimensions of the entire series of superior grinders, measured 

 in a straight line from the sharp, anterior enamel fold of p 2 to the pos- 

 terior, outer fold of m 3 , is 187 millimeters. The antero-posterior dimen- 

 sions of the individual teeth, following the outer curve of the series, but 

 inside the metastyle and parastyle, are : p 2 , 43.5 millimeters ; p 3 , 33 milli- 

 meters; p 4 , 31 millimeters; m 1 , 25 millimeters; m 2 , 26 millimeters, and 

 m 3 , 32 millimeters. This gives a total length of the series around the 

 outer curve, but inside the external styloid ridges, of 190.5 millimeters. 



Table showing comparative transverse Diameters of the Teeth of the Gladwin Horse. 



Gidley' s largest draft horse 



Gladwin fossil horse 



Differences 



Average of the 8 horses recorded in Gid- 

 ley's table 



Differences when the Gladwin horse "Is 

 compared with the average of Gid- 

 ley' s 8 horses 



P 2 - 



P 3 - 



P 4 . 



m 1 . 



m 2 . 



28.0 

 28.7 



.7 



30.0 



32.0 



2.0 



28.5 



32.5 



4.0 



28.0 



30.0 



2.0 



26.5 



28.5 



2.0 



24.8 



26.1 



26.9 



26.0 



25.4 



3.9 



5.9 



5.6 



4.0 



3.1 



23.0 



26.0 



3.0 



22.2 



There are a number of teeth from the Cox pit at Missouri Valley, and 

 one from Turin, which agree in dimensions with the larger teeth of the 

 Gladwin horse, and are. evidently from the same species, if transverse 

 diameters may be taken as a guide. These may be noted in tabular form 

 as follows: 



Catalogue 

 number. 



116 

 117 

 118 

 119 

 125 

 136 



Eeference to illustration. 



Plate 18, figures 1, 3 



Plate 18, figures 2, 4 



Plate 18, figure 6 



Plate 1 8, figure 5 



(Not illustrated) 



(From Turin, not illustrated) 



Trans- 



Antero- 



verse 



posterior 



diameter. 



diameter. 



33.0 



33.0 



33.5 



35.0 



32.0 



82.0 



31.5 



29.0 



31.0 



30.0 



33.0 



35.0 



Length. 



95 

 82 

 38 

 50 

 62 



