EDENTATA OF THE SANTA CRUZ BEDS. 75 



short and slender; metacarpal III is considerably longer and much' stouter, 

 while metacarpal IV is very short and broad and of subquadrate shape. 



The phalanges are different in every digit. The proximal phalanx of 

 digit I is extremely slender, but longer than in Zaedyus, indicating that 

 the pollex was less reduced than in the latter. In digit II the first and 

 second phalanges are very long and slender, while the ungual is small, 

 narrow and sharp-pointed ; digit II is the longest of the series. In digit 

 III the first and second phalanges are stout and very short, but the ungual 

 is very large, the largest in the manus. The proximal phalanx of digit IV 

 is extremely short, the second much longer and the ungual only slightly 

 smaller than that of digit II. All of the unguals have a long, shallow 

 fissure on the dorsal side near the distal end. 



Of the pelvis (Plate VI, fig. 10) only the ilia are known; they are inti- 

 mately united with the sacrum and diverge strongly toward the hinder 

 end, so that the pelvic opening is much wider at the acetabulum than in 

 front, from which it may be inferred that, as in Zaedyus, there was no pubic 

 symphysis. The peduncle of the ilium is shorter than in the recent genus, 

 slender and trihedral in form, and the anterior expansion is also shaped 

 as in the latter, but has a much less prominent crista; the ilio-pectineal 

 process is very large. 



The femur (Plate VI, fig. 11), while in general like that of Zaedyus, 

 differs from it in many ways ; the head is small and hemispherical, is set 

 upon a very short neck and has a large, deep pit for the ligamentum 

 teres ; the great trochanter rises much higher above the head than in the 

 recent genus, but is not so expanded antero-posteriorly, and has a thick- 

 ened free border, while the digital fossa is almost obsolete ; the second tro- 

 chanter is like that of Zaedyus, but is narrower, while the third is more 

 prominent, but narrower, and has a rather more proximal position. The 

 shaft is more slender and more cylindrical and the ridge which passes 

 down its external side from the third trochanter ends distally in a more 

 prominent process ; the conical tubercle just above the internal condyle is 

 more definite ; the rotular groove is shorter and the inner condyle is larger. 



The patella resembles that of Zaedyus, but is thinner and less rugose. 



The tibia (Plate VI, fig. 12) is proportionately longer and more slender 

 than in the existing genus and is much narrower at the distal end. On 

 the other hand, the fibula is somewhat heavier and much straighter, mak- 

 ing the arcade between the bones narrower. 



