6 ARKIV FÖR ZOOLOGI. BAND 7. N:0 10. 



It is especially^ the longitudinal diameter of all parts which 

 are so much larger in the southern Right Whale, while the 

 difference in width is less important. But when the length 

 of the bones is about tvvice as great, or more, in the Southern 

 Right Whale as in the Nordeaper, although the width is not 

 far from equal in both, this must result in quite a different 

 shape of the bones. This is especially striking with regard 

 to the femur which is not far from as broad as long in the 

 Nordcaper, and thus is much more decidedly rudimentary 

 in its appearance than in the Southern Right Whale. It 

 might be concluded from this that these bones have more 

 thoroughly löst their original shape and become even still 

 more reduced in the Nordcaper than in the Southern Right 

 Whale. 



Another difference is found in the mutual arrangement 

 of the bones. In the Nordcaper the ischium and the ilium 

 are situated in a straight line unlike the condition found in 

 its ally as mentioned above (conf. fig. 2). 



The femur of the Nordcaper forms nearly right angle to 

 the longitudinal axis of the pelvic bone, and, to judge from 

 the figure communicated by Abel, the femur appears to lie 

 in the same plane as the pubic bone. In the Southern Right 

 Whale on the other hand the angle which the femur forms 

 against the longitudinal axis of the ischium is considerably 

 less than 90"^ (conf. fig. 1 and 3), and the femur is by fibrous 

 tissue closely connected to the pelvic bone in such a way 

 that the plane through the broadest surface of the femur 

 forms nearly right angle to the broad surface of the pubic 

 bone. 



If the comparison is extended to the Greenland Whale 

 it will be seen that the Southern Right Whale with regard 

 to the shape and development of its pelvic rudiments in 

 certain respects more approaches this Arctic species than its 

 nearer relative the Nordcaper. The rudimentary pelvis and 

 hindlimbs of the Greenland Whale are well known thanks 

 especially to the beautiful researches of Struthers,^ who 

 has described these parts of no less than 11 specimens. Abel 

 has låter ^ compiled all facts about these organs of Balcena 

 mysticetus, so that they may be regarded to be pretty well 



^ Joiirn. Anat. Phvsiol. Vol. XV. London & Cambridge 1881. 

 ' 1. c. p. 156. 



