74 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 128 



material, as it is also in Eotylopus, is certainly recognized only in 

 Oromeryx plicatus of the earlier forms. In Protylopus petersoni this 

 character, though suggested, is not clearly determined because of ad- 

 vanced wear in teeth of critical material. 



Protylopus f annectens is further characterized by much greater size 

 than either P. petersoni or 0. plicatus, and the tooth enamel is com- 

 paratively smoother. P^ has three distinct roots, but the deuterocone 

 varies from weak to nearly as prominent as in P*. The cingulum may 

 be absent from the lingual margin of the upper molars but, if present, 

 is usually developed around the protocone rather than the metaconule. 

 However, a cusp (or cuspules) is present lingually between the 

 protocone and metaconule as in the earlier forms. 



MEASUREMENTS IN MILLIMETERS OF DENTITIONS IN REFERRED SPEOMENS OF 



Protylopus? annectens 



U.S.N.M. U.S.N.M. 



No. No. 



20290 20285 



Length of upper cheek tooth series, P*-M', inclusive 53.9 55.6 



Upper premolar series, P*-P^ inclusive 26.3 27.3 



Upper molar series, M*-M', inclusive 28.5 28.8 



C, anteroposterior diameter : greatest transverse diameter 4.0 : 3.2 



P\ anteroposterior diameter: greatest transverse diameter. 5.7: 2.5 6.2: 2.4 



P*, anteroposterior diameter : greatest transverse diameter. 7.70:2.8 7.8:2.5 



P^, anteroposterior diameter : transverse diameter* 7.3 : 6.0 7.8 : 4.7 



P*, anteroposterior diameter : transverse diameter 6.7 : 7.2 6.9 : 7.1 



M*, anteroposterior diameter : transverse diameter* 9.0 : 93 8.8 : 8.9 



M^ anteroposterior diameter : transverse diameter 9.9 : 10.8 10.2 : 10.7 



M^ anteroposterior diameter: transverse diameter ii.o: 12.0 ii.o: 12.0 



U.S.N.M. U.S.N.M. 



No. No. 



20149 20190 

 Length of lower cheek tooth series, C (at alveolus) -Ms, 



inclusive 69.0 64.3 



Length of lower cheek tooth series, P1-M3, inclusive 63.0 60.2 



Lower premolar series, P1-P4, inclusive 31. i 28.8 



Lower molar series, M1-M3, inclusive 32.2 32.0 



C, anteroposterior diameter : greatest transverse diameter. 4.0:2.8 4.3:2.8 



Pi, anteroposterior diameter : greatest transverse diameter. 4.8 : 2.5 5.3 : 2.5 



P2, anteroposterior diameter : greatest transverse diameter. 8.0: 2.5 6.6 : 2.3 



Pa, anteroposterior diameter: greatest transverse diameter. 8.5 : 3.0 7.8: 2.5 



P4, anteroposterior diameter : greatest transverse diameter. 8.1 : 4.2 y.y : 3.5 



Ml, anteroposterior diameter : transverse diameter of talonid 8.4 : 5.6 8.5 : 5.6 



M2, anteroposterior diameter : transverse diameter of talonid 9.8 : 6.1 9.9 : 6.2 

 M3, anteroposterior diameter : transverse diameter of trig- 



onid 14.8 : 6.8 14-5 : 6.8 



a, Approximate. 



• Measurements of posterior upper premolars are taken anteroposteriorly across outer por- 

 tion and transversely perpendicular to outer margin. Those of upper molars are talcen 

 anteroposteriorly perpendicular to anterior margin and transversely across anterior portion 

 of tooth. 



