96 PATAGONIAN EXPEDITIONS! PALEONTOLOGY. 



Metacarpal V has not been found, but the facets of the adjoining bones 

 prove its presence. 



In the only known individual with fairly well preserved feet, the pha- 

 langes were so scattered and confused, that I cannot be entirely confident 

 that the arrangement given in the plate is in all respects accurate. In 

 the pollex, the proximal phalanx is slender and longer than metacarpal I, 

 but far shorter than in Proeutattis ; in digit II it is somewhat shorter and 

 very much heavier, with a well-developed concave trochlea at each end, 

 while in digit III it is still shorter and heavier and has a very prominent 

 median dorsal "beak" on the proximal end. 



The second phalanx of digit II is like the first of the same digit and of 

 nearly the same length; in digit III it is, if correctly identified, shorter 

 and more depressed, while in digit V it is very short, broad proximally 

 and narrow distally. 



The ungual phalanges are like those of Proeutatus, but are shorter, 

 more bluntly pointed and none of them is cleft at the tip ; that of the 

 pollex, in correlation with the reduction of the whole digit is relatively 

 much smaller than in any of the preceding genera. 



Digit II is the longest of the series, III is somewhat shorter, IV con- 

 siderably so, while I and V are greatly reduced. 



The femur (Plate XVI, fig. 12) is very characteristic and quite unlike 

 that of any other Santa Cruz genus, differing especially from that of 

 Proeutatus; the head is rather small, low, depressed and sessile; the fossa 

 for the round ligament is large and shallow ; the great trochanter is of 

 only moderate size and smaller even than in Prozaedius,pR& has a minute 

 digital fossa ; the second trochanter is peculiar only in having a more dis- 

 tal position than in the other genera, while the third is more proximal, 

 broader proximo-distally and much less prominent. The shaft is slender 

 and subcylindrical, having proportions not unlike those in Prozaedius; the 

 distal expansion is very moderate, the external crest is almost obsolete 

 and the hook-like process above the inner condyle is very small ; the 

 rotular groove is very broad and shallow and the condyles are of unequal 

 size, though the difference is less than in Proeutatus, while the intercon- 

 dylar notch is much wider. 



In the young animal tibia and fibula (Plate XVI, fig. 13) are separate, 

 but they are, as usual, coossified in the adult. The tibia is somewhat 

 shorter than the femur and is much more slender than in Proeutatus; the 



