EDENTATA OF THE SANTA CRUZ BEDS. 97 



proximal condyles are widely separated and there is no spine ; the shaft 

 is much compressed and, for most of its length, deeply concave externally, 

 with very faint interosseous crest ; the cnemial process is far less prominent 

 than in Proeutatus. The external facet for the astragalus is larger and 

 more concave than the internal, from which it is partly separated by a 

 long and broad, but very shallow sulcus, which invades the articular 

 surface from the anterior side and corresponds to a very shallow 

 sulcus on the trochlea of the astragalus; the internal malleolus is 

 small, but larger than in Proeutatus, while the posterior median tongue is 

 smaller. 



The fibula is quite different from that of the other Santa Cruz arma- 

 dillos, having a very much more slender and subcylindrical shaft, instead 

 of the usual plate-like form, and has no interosseous crest ; the distal end 

 forms a prominent and heavy external malleolus, which has no contact 

 with the calcaneum. 



Although not departing from the armadillo type of structure in any 

 radical way, the pes (Plate XVI, fig. 14) is different from that of any other 

 known genus. The proportions of the digits are most like those of Tatu, 

 the foot being functionally tridactyl ; the three median digits are long, 

 slender and of nearly equal length, while the laterals are so reduced that 

 they can have had little or no function. While this is the plan upon 

 which the pes of Tatii is constructed, that of Peltephihis receives a very 

 different appearance from the long, slender median digits (II, III and IV) 

 and the hoof-like ungual phalanges. 



The astragalus resembles that of Proeiitatus, with a number of differ- 

 ences ; thus, the broad, shallow trochlea is invaded by a sulcus from the 

 distal side, which is not present in the latter ; the fibular facet is much less 

 produced externally, and the external calcaneal facet is very different, being 

 nearly proximo-distal in direction, instead of very oblique ; it has no such 

 external prolongation and is separated by a broader sulcus from the sus- 

 tentacular facet. 



The calcaneum has a compressed tuber, with almost straight and par- 

 allel dorsal and ventral borders, like that of Sfegofherimn, but much 

 shorter, and very different from the broad depressed tuber of Proeutatus; 

 the external astragalar facet is much less oblique than in the latter and 

 there is no articulation with the fibula ; the sustentaculum is very prom- 

 inent and its facet small. 



