59 



The pelvis shows the conversion of the ischiadic notch into a 

 foramen by the anchylosis of the ischia with the posterior sacral 

 vertebrae, and the union of the ossa pubis at a short anteriorly pro- 

 duced symphysis. The ilia are extraordinary for their vast breadth, 

 and the thickness of the rugged labrum ; indicative of the enormous 

 muscular forces, of which this conspicuous part of the skeleton was 

 the centre. 



The femur is hardly less remarkable for its breadth and strength. 

 The head is devoid of an impression for the ligamentum teres: but 

 from the dimensions of the hemispheroid cavity receiving it, the 

 author calculates that the muscles are aided in retaining the head 

 of the femur in its place by an atmospheric pressure, with the baro- 

 meter at 30 in., of not less than 660 pounds. At the distal end of 

 the femur there is a great angular projection above the outer con- 

 dyle. The rotular surface is continuous with that upon the outer 

 condyle, but not with the inner one. The tibia and fibula are anchy- 

 losed together at both their extremities. Besides the patella in front 

 of the knee-joint, there is a sesamoid ' poplitella' behind, wedged 

 between the outer condyle and the tibia; which was doubtless im- 

 bedded at its base in the femoro-tibial articular capsule, and gave 

 insertion to the tendon of the popliteus muscle. This sesamoid is 

 not to be confounded with the ' fabella,' developed in many quadru- 

 peds in the origin of the gastrocnemius, behind one or both condyles 

 of the femur. The most peculiar feature in the tibia of the Mega- 

 therium is the form of the distal articular surface: especially the 

 large and deep hemispherical excavation on the inner part of that 

 surface for an unusually secure interlocking of the foot to the leg. 



The bones of the tarsus are six in number in the Megatherium, 

 and the astragalus offers corresponding peculiarities vv'ith those of 

 the tibia with which it is articulated, and also remarkable modifica- 

 tions for the articulation of the naviculare and calcaneunl. In the 

 calcaneum,the length and strength of the hinder prominence forming 

 the great lever for the extension of the foot, are amongst its most 

 striking characteristics. These, with those of the other bones of 

 the tarsus, are minutely detailed. There is no digit answering to 

 the great toe or 'hallux,' nor any trace of the ' os cuneiforme' for 

 that toe. The innermost of the 'ossa cuneiformia' answers to the 

 middle one, and if any rudiment of the second toe ever existed in- 

 dependently, it has coalesced with that cuneiform bone: but this 

 cannot be supposed to represent both middle and internal cuneiform 

 bones and their digits blended together, as Cuvier supposed. There 

 are no little bones missing from the inner side of the middle cunei- 

 forme, as Pander and D'Alton conjectured. The first or innermost 

 distinct metatarsal bone is that of the toe answering to the third, or 

 digitus medius, in the pentadactyle foot : it is a short thick irregular 

 Wedge-shaped bone, with a large triangular concave base for the 

 ' ecto-cuneiforme'; a semicircular flattened surface on the outer side 

 for the fourth metatarsal, and a small semi-elliptic flat surface on 

 the inner side for the ' meso-cuneiforme'. The distal end of tlie 

 bone presents a strong median vertical obtuse ridgcj dividing two 



