OSTEOLOGY AND DENTITION OF HTLOMTS. 465 



xiphosternum is a dorso-ventrally flattened rod of bone, slightly expanded at its two 

 extremities, and about the length of the first and second mesosternal pieces, with an 

 obscure longitudinal ridge on its outer surface. 



The humerus (fig. 14) is a rather short bone, only a very little shorter than the ulna. 

 It is strong, and marked by a not very prominent deltoid ridge, in which region the 

 bone is slightly laterally compressed. It has a rather large supracondylar foramen, 

 which is wider behind than in front. The ectocondylar ridge does not extend on to 

 the shaft, but forms a short eminence, with the surface external to it concave. The 

 anconeal fossa is rather shallow. 



The shaft of the radius arches over the ulna, but the bones are separated by only a 

 very narrow interval. The ulna is a third the length of the radius longer than that 

 bone. The olecranon is large, strong, and incurved, externally convex, and internally 

 concave. Its posterior extremity is divided into two surfaces, there being a lower 

 rough surface for the attachment of the triceps extensor muscle. 



The carpus is provided with a scapholunare and os intermedium and a large pisiform 

 bone, resembling in miniature the pisiform of a Bear. The longest metacarpal bone is 

 one third the length of the ulna. The first metacarpal is but little longer than the 

 second, which reaches only to the anterior extremity of the middle third of the third 

 metacarpal, which is of the same length as the fourth, which, in its turn, is twice as long 

 as the fifth. 



The innominate bone (fig. 16) is long and narrow, with an elongately oval obturator 

 foramen, with the very small symphysis pubis posterior and inferior to the foramen, 

 with the tuberosity of the ischium nearly immediately above it, but the two sepa- 

 rated from each other by the greatest width of the innominate bone, which here forms 

 a triangular, externally concave, surface, with its posterior margin concave from behind 

 forwards. The outer surface of the ilium is concave ; and the spine of the ischium 

 forms a well-marked lesser sciatic notch with the smooth surface for the tendon of the 

 obturator internus muscle well displayed. 



The femur (fig. 17) is short and strong, with the muscular ridge continuous with the 

 great trochanter, and passing down one half the length of the bone. The neck is very 

 well defined. The patella is an elongated oval. 



The tibia and fibula (fig. 18) are completely united throughout one half of their 

 extent ; and in front, at theii' united extremity, there is a rather deep pit. The outer 

 surface of the tibia, immediately below the knee-joint, forms a sharp ridge of bone, 

 which is folded outwards with a deep concavity external to it. The fibula is very deli- 

 cate ; and where not united to the tibia, the two bones enclose a very much elongated 

 oval space. In the specimen before me the epiphyses of the upper extremity of the two 

 bones have completely united, while the upper extremities of the shafts are distinct. At 

 the lower end the epiphyses of the two bones have disappeared. The calcaneum is a 

 long rod-like bone, with its under surface rounded from side to side, but longitudinally 

 quite flat, projecting only a short way behind the bones of the lower leg. 



