EDENTATA OF THE SANTA CRUZ BEDS. 249 



and the shaft is more slender; the distal facet for the tibia is smaller and 

 that for the astragalus more nearly plane. 



The astragalus is less grooved than in the last named species, which is 

 due principally to the smaller development of the inner condyle ; the neck 

 is distinctly shorter and the internal calcaneal facet is smaller and some- 

 what better demarcated from the navicular facet on the plantar side of 

 the neck. 



MEASUREMENTS. 



Femur, length from head 1 50 Tibia, thickness of distal end 020 



" " " great trochanter. . . .150 Fibula, length 109 



" width of proximal end 056 " width of proximal end. 014 



" " " distal end over tuberosi- " thickness of proximal end 017 



ties 048 " width of shaft in middle 007 



" " " condyles .045 " thickness of shaft in middle 009 



Tibia, length 119 " width of distal end 020 



" width of proximal end 046 " thickness of distal end 018 



" thickness of proximal end 035 Astragalus, length 029 



" width of shaft in middle 018 " width of trochlea 020 



" thickness of shaft in middle 012 " " " distal end 015 



HAPALOPS GRACILIDENS Ameghino. 



(Plates XLIV, Figs. 2, 2", 2 b , 2" ; XLV, Fig. 4.) 



Hapalops gracilidens Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, 



P- 3i7- 

 In the Princeton collection, this species is represented by two skulls, 



without mandibles, which were found by Mr. Hatcher, one (No. 15,529) 

 at Killik Aike, and the other (No. 15,525) at Lake Pueyrredon ; the latter 

 has been considerably distorted by lateral pressure, which much exag- 

 gerates the difference between the two specimens. 



The teeth are strikingly small even in proportion to the small size of 

 the skull, and this is especially true of the individual from Lake Pueyrre- 

 don. The first upper tooth (-) is subcylindrical and relatively large, its 

 alveolus forming quite a prominence upon the side of the face ; the dia- 

 stema is short and the molariform teeth (-".-) are of transversely rectangu- 

 lar shape ; - is slightly larger than the others, while - is extremely 

 small, particularly so in the type. The teeth of the two sides form paral- 

 lel rows. 



