482 THE WASATCH FAUNA. 



the head, and hence oblique to the long axis of the distal extremity. They 

 are deep and with rounded fundus. The posterior apex of their dividing 

 ridge is equally produced with the anterior angle, which is just exterior to 

 the end of the dividing ridge. The internal malleolus is truncate below, 

 and a little more produced than the two angles in question. The inner 

 side of the internal malleolus is nearly flat, and but shallowly concave. 



The head of the fibula is expanded anteroposteriorly. The shaft is 

 slender and subround in section. The distal extremity is less expanded 

 than the proximal, and its transverse and anteroposterior widths are equal. 

 It has two distal faces; one oblique for the astragalus, the other transverse 

 and free. The tendinous groove of its external face is only marked by a 

 short prominent ridge on its anterior border. 



Measurements of posterior limb. m. 



Total length femur from head 133 



Length to line of middle of third trochanter 049 



Length to internal rotular crest 106 



Diameters of head ^ ^""S •<'^^ 



c short at middle 013 



I proximally 036 



Total width femur < at third trochanter .024 



( below third trochanter 013 



Greatest width of condyles 028 



Depth of condyle at inner rotular crest 038 



I longitudinal , 020 



Diameters of patella < transverse 015 



( anteroposterior above Oil 



Total length of tibia 143 



; anteroposterior at internal cotylus 034 



Diameters of the head \ anteroposterior at popliteal notch 025 



( transverse 030 



Anteroposterior diameter of shaft at distal third 010 



Diameter of distal end of tibia ^'^°t®™P''^*«"°^(S^«''t««*) 018 



( transverse 018 



Length of fibula 128 



Proximal diameter anteroposteriorly 014 



Diameter of middle of shaft 005 



Distal diameter ^ ^°*«^°PO«t«"»' O^l^ 



( transverse 010 



Besides its greater slenderness, the tibia of this species differs from that 

 of P. primcevus in the greater obliquity of the astragalar grooves. In the 

 latter species, the internal malleolus is more protuberant, and not truncate, 

 as in the P. vortmani; and the anterior face of the distal end is flatter. 



The posterior foot is almost entirely preserved. The astragalus is a 

 diminutive of that of P. primoevus, having the trochlear groove profound 

 and the neck elongate. It differs from it in having the trochlear ridges less 



