E. L. Troxell — American Bothriodonts. 339 



tip of the protoconid. On each side of the posterior ridge 

 are depressions bounded below by the basal cingulnm. 

 The diameters are 20 X 9 mm. P2 is not preserved, but 

 the two rootlets indicate its small narrow form. Pi was 

 entirely lacking, or was set near the canine in front of a 

 long diastema, as is indicated by other specimens at hand. 

 The canine (fig. 7 B) has a very unusual form, which 

 may be considered a flattened cone, with three strong- 

 ridges from the front, inner and back sides joining at the 

 apex. Its diameters are 14.6 and 12 mm., the enameled 

 crown being 22 mm. long. 



SUMMAKY. 



The weight uf the evidence seems to show that 

 Aymard's genus Bothriodon precedes Ancodus Pomel and 

 Hyopotamus Owen in spite of statements to the contrary. 



Our American species, distinct from European forms 

 of this group, may be placed under the following gen- 

 era: ^pinacodon, Elomeryx, Heptacodon, and Octaco- 

 don. The first of these is new and is made to include 

 A. deflectus (Marsh), A. americanus (Leidy), and A. 

 rostratus (Scott), species commonly classed under Anco- 

 dus. 



One new subspecies is here described under the name 

 Elomeryx armatus angustus, and the very complete skull 

 is figured. 



