HISTORY OF MARINE MAMMALS—ABEL. 495 
will doubtless be possible to bring this problem to solution some time 
soon. 
If we review the results of our investigations, we see that the 
Fic. 25.—Left pelvic bone of the Bowhead or Arctic right whale, Balaena mysticetus L., 
seen obliquely from without. About 7; natural size. From left to right, the first three 
figures make it intelligible how the present position of the pelvic bone of the Bowhead 
was assumed. The upper end of the ileum has rotated backward, until the hip-bone 
lies horizontally. The anterior end is toward the left, the posterior toward the right. 
IL., ileum; P., pubis; IS., ischium; A., acetabulum; F., femur; T., tibia (cartilaginous). 
marine mammals do not form a single group, but belong to series of 
entirely different forms, not closely related. 
The whales originated from very old land carnivores, the sea-cows 
Fic. 26.—Left pelvic-bone of the Common Finback, Balenoptera physalus L., seen ob- 
liquely from without. About ;; natural size. The left and middle figures show how the 
position of the hip-bone of finback assumed its present position. The upper end of 
the ileum has turned downward forwards, so that the bone is horizontal. The anterior 
end is toward the left, the posterior toward the right. Abbreviations as in Fig. 25. 
from elephant-like pachyderms, the sea-otter from ordinary otters, 
and the seals probably from bears. 
We have seen that, in spite of many similarities in the form of the 
body, the whales are not allied to the ichthyosaurs; also among 
marine mammals there is a series of corresponding lines. Thus we 
