0. C. Marsh — Description of Tertiary Artiodactyles. 273 



These remains prove that the animal they represent belonged 

 to a distinct family, which may be called the LeptochmridcB. 

 The type specimen of the present species is from the Miocene 

 of South Dakota. 



Calops cristatus, 1894. 



The peculiar Artiodactyle described under the above name, 

 in a late number of this Journal (p. 94), had many features of 

 interest besides those mentioned in the original description. 

 Some of these are as follows : 



The brain was comparatively well developed, and an 

 unusually large part of the cerebral lobes was covered by the 

 parietals. The frontal region of the skull between the orbits 

 was more or less concave. The antorbital depressions extend 

 well forward. There is a diastema between the upper canine 

 and the first premolar, and between the first and second pre- 

 molars. The canines above and below are small. The first 

 lower premolar appears to be wanting. The second and third 

 premolars have secant crowns, much elongated fore and aft. 

 The postglenoid process is quite small, but the paroccipital is 

 large and robust. The lower jaw has a very short coronoid 

 process, and the condyle is sessile. The angle of the jaw is 

 well rounded and somewhat dependent. 



Pliocene Artiodactyles. 

 31. 32. 



Figure 31. — First and second lower molars of Platygonus rex, Marsh ; top view. 

 FiGintE 32. — Last lower molar of same species ; young tooth ; top view. 

 Both figures are natural size. 



Platygonus rex, sp. nov. 



The present species is the largest of the genus yet dis- 

 covered. The type specimen is represented natural size, in 

 figure 31 above. In figure 32, a last lower molar of the same 

 species is shown, but it is a young tooth which had not yet 

 come into wear. The peculiarity of these molar teeth, aside 

 from their size, is that the crowns are mainly composed of well- 

 rounded, conical tubercles, few in number, and placed sys- 

 tematically. The crowns of the first and second molars are 

 each composed of four large cones, nearly equal in size, and 

 the last molar has five. 



