THE SKELETON IN MAMMALIA. THIGH AND SHIN. 517 



7. second digit of pes. 14. radius. 



8. ungual phalanx of fifth digit 15. ulna. 



of pes. 17. unciform. 



9. calcaneum. 18. cuneiform. 



10. postscapular fossa. 20. lunar. 



11. prescapular fossa. 21. first metacarpal. 



12. coracoid process. 22. fifth metacarpal. 



13. humerus. 



narrow and has a small iliac surface. The ischial tuberosities 

 are large in the old world monkeys. 



THE THIGH AND SHIN. 



In the MONOTREMATA the femur is short, rather narrow in 

 the middle, and expanded at each end. The great and lesser 

 trochanters are large and about equally developed, but there is 

 no third trochanter. The fibula is very large and is expanded 

 at its proximal end, forming a flattened plate much resembling 

 an olecranon. The patella is well developed. 



In the MARSUPIALIA there is no third trochanter to the 

 femur, the fibula is well developed but not the patella as a 

 general rule. Notoryctes has a femur with a prominent ridge 

 extending some little way down the shaft from the great tro- 

 chanter ; the tibia has a remarkably developed crest, and the 

 fibula has its proximal end much expanded and perforated; 

 there is an irregularly shaped patella closely connected with 

 the proximal end of the tibia. 



EDENTATA. In the Sloths the leg bones are all long and 

 slender. The femur has no third trochanter, and the fibula is 

 complete and nearly equal in size to the tibia. In the Mega- 

 theriidae the leg bones are extraordinarily massive, the cir- 

 cumference of the shaft of the femur in Megatherium equalling 

 or exceeding the length of the bone. There is no third tro- 

 chanter in Megatherium. In most of the remaining Edentata 

 the leg bones are strongly developed. The femur in the Arma- 

 dillos and Aard Yarks has a strong third trochanter, and the 



