100 



THE DESEADO FORMATION OF PATAGONIA 



the two rows of carpals to alternate, but this is not ad- 

 vanced to any considerable degree. The trapezium is 

 entirely isolated from the other carpals, and lies as a flat- 

 tened scale, on the side of the upper end of Mc. II. 



The metacarpals are closely crowded together, making 

 a compact foot with very little freedom of motion in its 

 upper part. The three carpals are of nearly equal length, 

 though the third is slightly heavier and longer than the 



Fig. 60. Digit 4 of Rhynchippus from 

 the side — 1/2 natural size. 



Fig. 61. Pair of se- 

 samoids under Mc. 

 IV — 1/2 natural size. 



others, but there is no tendency toward a further reduction 

 of the toes. 



Metacarpus II, length 

 Metacarpus III, length 

 Metacarpus IV, length 



67 mm. 

 74 mm. 

 69 mm. 



Under each metacarpel are two small sesamoid bones 

 which lie either side of the low crest of the metacarpus. 

 The toes are all short, with flattened articular ends, which 

 are cut under in a very oblique manner. The second pha- 

 lanx is much shorter than the others, while the distal, or 

 ungual phalanx, is the longest and highest of the three. 

 Each ungual phalanx is cleft by a deep narrow notch, much 

 more suggestive of a claw than a hoof. The phalanges of 

 all the toes are subequal in size, so that the measurements 

 of the middle digit are given. 



First phalanx of digit III, length 

 Second phalanx of digit III, length 

 Third phalanx of digit III, length 



\2 mm. 



8 mm. 



16 mm. 



