SYNOPSIS OF TIIK VERTEBRATE FAUNA OF THE PUERCO SERIES. 335 



The inferior molars are referred to this species because of the large size of the 

 premolars, which approach in dimensions those of the M. zittelianus. The first has a 

 low wide heel, and no anterior basal angle. The fifth cusp exists as a cusp on the m. 

 i and ii. The curved border of the heel in these teeth is more elevated than in the 

 M. minimus on the inner side, so as to enclose a dee[) basin, which is much better 

 defined than in M. minimus. In the third and fourth individuals, where the last inferior 

 molar is preserved, this tooth is smaller than the m. ii, and both of these teeth have 

 the fifth cusp present, but small, and appressed as a small twin on the anterior face of 

 the fourth. This occurs also in the M. acolytus, and I do not believe that the char- 

 acter is constant. 



Measurements. -'/. 



LengUi of superior molars (last estimated) Oil 



( anteroposterior ." 005 



Diameters m. ii < „r,rr 



I transverse W)jo 



anteroposterior 004 



Diameters m. i < [.^..^ 



transverse W4o 



(a. 



Diameters p. ni. i ■ 



I antoropostt-rior 0045 



' transverse 000 



Length inferior true molars (sp. 2) 0125 



" p.ni.i 005 



Depth ramus at m. ii 0075 



The typical specimen is from the lowest beds of the Piierco. D. Baldwin. 



MiocL.KNUS ACOi-YTCs Copc. Ili/opsodus acoli/lus Cope ; Proc. Amer. Pliil. Soc, 1883, p. 4(13 ; Tertiary Vcrtebrala, 

 1885, p. 238, PI. XXIII d, figs. 5-fl. 



Additional specimens of this species show that it differs fi'om the M. minimus in 

 the presence of a strong external cinguliiin of the superior true molars, and the less 

 reduced size of the last inferior molar. A single specimen, figured as above, displays 

 the first two true molai-s and the fii-st premolar above, and both the last inferior molars 

 of the same skull. From the M. turr/idunculus this species is easily distinguished by 

 the small first and second premolars in both jaws. A damaged skull, without lower 

 jaw, shows this charactei-, as well as the type, and also that the fourth superior pre- 

 molar has but one root, and is of small size; also that the canine is well developed 

 and has a vertical direction. The second superior premolar has an internal cingulinn, 

 but no cusp. 



Measurements of Skull. M. 



Length of superior dental series 0353 



true molars 009 



Width between superior canines Oil 



Five specimens ; all lioni the Upper Puerco except one, and the specific refer- 

 ence of this one is uncertain. 

 A. p. s. — VOL. xvr. 2q. 



