EDENTATA OF THE SANTA CRUZ BEDS. 53 



expands to form the trochlea, which is smooth, slightly convex and with- 

 out carina. 



Metacarpal II is very much longer and heavier ; the proximal end is 

 narrow, but thick palmo-dorsally, and is covered by the trapezoid facet, 

 which is quite deeply grooved in the median line and thus divided into 

 two parts ; there is no contact with the magnum, but on the radial side a 

 connection with the trapezium. The shaft, which is rather narrow and 

 thick proximally, becomes broader and thinner distally; the trochlea is 

 very low and has a small palmar carina. 



Metacarpal III is the longest of the series ; it resembles metacarpal II 

 in shape, but is much stouter, a difference which is more pronounced than 

 in Dasypus ; the proximal end has a deeply concave facet for the magnum, 

 with a projection on each side of it, one of which articulates with the 

 trapezoid and the other with the unciform ; the shaft is heavy and of 

 nearly uniform width, except for the broadening of the distal end ; the 

 trochlea is veiy low, concave transversely, and has a small keel. 



Metacarpal IV is much shorter than metacarpal III, but relatively longer 

 than in Dasypus and of a different shape ; it is very heavy, much the stoutest 

 of the whole series ; the proximal end has a broad contact with the unci- 

 form and is additionally widened by a projection which fits into a notch on 

 the shaft of metacarpal III. The shaft is very heavy, slightly constricted 

 above the middle and wider at the ends ; the trochlea is peculiar in having 

 two concavities, separated by a ridge. 



Metacarpal V is much the shortest of all and of a very modified shape, 

 being pyramidal, with base turned to the radial side and apex toward the 

 ulnar ; as in other armadillos, its articulation with the unciform is lateral 

 and proximally it connects with the pyramidal. 



The phalanges are much specialized and differ in almost every digit, 

 though those of digits II and III are quite similar. The proximal phalanx 

 is much longer and more slender in the pollex than in the other digits and 

 is less reduced than that of Dasypus ; the surface for the trochlea of meta- 

 carpal I is ungrooved and nearly plane. In digit II this phalanx is shorter 

 and much heavier, and is shorter, stouter and less compressed than in the 

 modern genus ; the proximal trochlea is deeply invaded from the palmar 

 side by a groove for the metacarpal carina, almost dividing it into two 

 facets. In digits III and IV the first phalanx is broad and far shorter than 

 that of digit II, and is considerably larger in the third digit than in the 



