EDENTATA OF THE SANTA CRUZ BEDS. 33 



The hind-foot (Plate IV, fig. 7), which belongs to No. 15,565, differs 

 in many respects from any other pes that has been found in the Santa 

 Cruz beds. 



The astragalus has the short, broad, depressed form usual in the arma- 

 dillos, but the trochlea is more deeply grooved than in the other Santa Cruz 

 genera and is divided into two very unequal condyles, of which the ex- 

 ternal one is much the broader, while the internal is higher and more con- 

 vex ; the fibular facet is somewhat everted at the plantar edge, and the 

 external calcaneal facet is very large and concave and much produced ex- 

 ternally, while the sustentacular facet is small, of elongate, subquadrate 

 shape and entirely isolated from the other. The neck is short, broad and 

 depressed and has a shallow depression on the dorsal side ; the head is 

 transversely convex, very low in the dorso-plantar dimension. 



The calcaneum is conspicuously different from that of any other known 

 Santa Cruz armadillo ; among existing genera, it most resembles that of 

 Tatu. The tuber is very elongate, longer than in the latter, and com- 

 pressed, but deep in the dorso-plantar diameter, with no expansion at the 

 free end ; the dorsal border is nearly straight, the ventral somewhat sinu- 

 ous ; at the proximal end is a very short, but distinct, tendinal sulcus. The 

 external astragalar facet is short, but very broad transversely, projecting 

 out beyond the side of the tuber, and its outer end bears a small facet for 

 the fibula, which is continuous with the fibular facet on the astragalus, 

 when the two bones are in position. The sustentaculum is very promi- 

 nent, but narrow and pointed and bears a small, isolated, subcircular facet 

 for the astragalus. The cuboid facet is small and but slightly concave, 

 narrowing to ward the plantar side; external to it is a large, rugose tubercle. 



The navicular is broad, short and thin and is not extended up on the 

 inner side of the astragalar head, as it is in most armadillos. On the plantar 

 side is a prominent, hook-like process and on the distal end are three well- 

 distinguished facets for the cuneiforms ; the cuboid surface is a narrow 

 band on the plantar side. 



The entocuneiform is shaped much as in Dasypus, being relatively large, 

 but thin and scale-like ; its facet for the navicular is concave, oblique and 

 somewhat warped ; that for metatarsal I is saddle-shaped. 



The mesocuneiform is small, but not so much reduced as in Dasypus or 

 Tafti, and its principal diameter is the dorso-plantar; the exposed dorsal 

 surface is nearly square and both proximal and distal ends are concave. 



