PRIMATES. In Man and the Anthropoid Apes the pelvis is very large and wide, and the ilium has much expanded iliac and gluteal surfaces. The symphysis is rather short and formed by the pubis alone. The acetabulum is deep and the obturator foramen large, and there is frequently a well-marked ischial tuberosity. In the lower Anthropoidea the ilium is long and narrow and has a small iliac surface. The ischial tuberosities are large in the old world monkeys. [Illustration FIG. 108. LEFT ANTERIOR AND POSTERIOR LIMB AND LIMB GIRDLE OF _Uintatherium mirabile_. The anterior limb is to the left, the posterior to the right × 1/10. (From casts, Brit. Mus.) 1. ilium. 2. head of femur. 3. great trochanter. 4. patella. 5. fibula. 6. tibia. 7. second digit of pes. 8. ungual phalanx of fifth digit of pes. 9. calcaneum. 10. postscapular fossa. 11. prescapular fossa. 12. coracoid process. 13. humerus. 14. radius. 15. ulna. 17. unciform. 18. cuneiform. 20. lunar. 21. first metacarpal. 22. fifth metacarpal.] 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 trochanter; 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 Megatheriidae the leg bones are extraordinarily massive, the circumference of the shaft of the femur in _Megatherium_ equalling or exceeding the length of the bone. There is no third trochanter in _Megatherium_. In most of the remaining Edentata the leg bones are strongly developed. The femur in the Armadillos and Aard Varks has a strong third trochanter, and the tibia and fibula are both large and are commonly ankylosed together at either end. The limb bones are very massive also in the Glyptodonts. SIRENIA. In no living Sirenian is there any trace of a hind limb, but in _Halitherium_ a vestigial femur is found, which articulates with the pelvis by a definite acetabulum. [Illustration FIG. 109. LEFT FEMUR OF AN OX (_Bos taurus_) (to the left) AND OF A SUMATRAN RHINOCEROS (_R. sumatrensis_) (to the right). × 1/6. (Camb. Mus.)