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PROCEEDINGS OF THE NATIONAL MUSEUM 



The upper molars, No, 16189 (fig. 21, &), of which only M^ and M- 

 are known, closely resemble those in E, ditrigonus in structural de- 

 tails, but with perhaps a somewhat weaker protostyle. The postero- 

 external portion of M^ shows the cuspate condition characterizing 

 upper molars in Ectoeonus. The mesostyle, metastyle, and the large 

 cusp external to the metacone are developed to about the same extent as 

 in E. ditrigonus; however, the parastyle on M^ appears weaker than in 

 E. ditrigonus. P*, No. 16188 (fig. 21, c), is of about the same width, 

 or perhaps slightly wider transversely than M^, and differs from that 



Figure 21. — Ectoeonus symbolus, new species: a, Portion of left ramus of mandible with 

 M2-M3 (U.S.N.M. No. 16190), lateral and occlusal views; b, M} and portions of P* 

 and M2 (U.S.N.M. No. 16189), type specimen, occlusal view; c, P^M^ (U.S.N.M, No, 

 16188), occlusal view. X 1}4. Wagonroad Paleocene, Utah. 



in E. ditrigonus in the absence of an accessory cusp anteroexternal 

 to the deuterocone, in about the position occupied by the protoconule 

 in the molars. 



The lower jaw material consists of three specimens which together 

 give a representation of the dentition from Po to M3, except for Mi. 

 The premolars are relatively large, particularly Pa, No. 16213, but 

 become relatively narrower posteriorly than in E. ditrigonus. The 

 molars, No, 16190 (fig. 21, a), are smaller and relatively narrower 

 than in E. ditrigonus, and there is but the slightest suggestion of a 

 second paraconid or parastylid ; however, the presence of this cuspule 

 is not invariable in E. ditrigonus. Mj and M3 in Ectoeonus symbolus 

 are otherwise similar to those in E. ditrigonus in having low blunt 

 cusps and a heavy external cingulum. 



