OSTEOLOGY 155 



which then passes craniad to the acetabulum. The pubo- 

 ischial articulation is not shown by any specimen at hand, 

 and its precise position is inferred; but the other articulations 

 of the four bones are clearly traceable in skeletons of two 

 young individuals, although they are entirely obliterated 

 in those that are fully adult. 



There are thirty muscle and tendon attachments upon the 

 innominate, and it is impossible, therefore, to interpret the 

 effects which many of them have had upon the bony frame- 

 work. The length of the pelvis varies from 44 to 48 per cent 

 of the functional length of the hind leg, and there is no sub- 

 generic variation in this respect. The length of the ilium, 

 measured from the cranial border of the acetabulum, is from 

 57 to 61.6 percent of the length of the innominate, and the 

 ischial depth, from 32.9 to 38.1 per cent of the same. These 

 measurements, even the last, exhibit surprisingly little 

 individual variation, but the differences in the precise con- 

 figuration of the details are great, and in fact hardly any two 

 innominates are exactly alike. This is especially noticeable 

 in the shape of the pelvic arch, which varies individually in 

 both sexes from V-shaped to U-shaped. So far as known the 

 pelvic arch is always closed by the symphysis pubis in the 

 present genus. The differences shown in the degree of di- 

 vergence of the cranial portion of the ilia are also well nigh 

 infinite, as is the precise position of the articulation with the 

 sacrum, as previously noted. Thus the terminations of the 

 transverse processes of the sixth lumbar vertebra may be 

 situated slightly craniad or considerably caudad to the 

 cranial ends of the ilia. The arc of the lateral ridge 

 extending from the spine may have a relatively slight or a 

 sharp curve, the latter circumstance causing the spine to 

 project sharply laterad. These variations seem to be purel}^ 

 individual. 



Attention should again be called to the fact that especially 

 in the case of the innominate, many of the muscle attach- 



