HUMPBACK WHALK. 



297 



Measurements of a Humpback Skull (M.C.Z. 6177). 



cervical this canal, at its inception, is open on account of the failure of the dorsal and ventral 

 processes to unite laterally. In the third, fourth, and fifth vertebrae the ventral processes are 

 successively reduced, and on the sixth and seventh are lacking entirely. In the Finbacks 

 the canal is usually closed throughout the seven cervicals, though occasionally in the last one 

 or two the ring is incomplete. 



In an immature specimen from Provincetown, True found the last neural spine to be on the 

 40th vertebra and the last transverse process on the 38th. (For detailed measurements and 

 proportions of the vertebrae see Struthers, 1889, p. 61, and True, 1904, p. 234.) 



The dorsal spines of the vertebrae are rather narrower in lateral aspect than in the Fin- 

 back, with less tendency to expansion at their tips. The transverse processes similarly are 

 much loss expanded terminally and are less flattened. 



The chevron bones are said to be only nine in a young specimen from Cape Cod (U. S. 

 Nat. Mus. 16252), but there may possibly be two or three more. 



The ribs are in general shorter and stouter than in the Finback, except the two first, 

 which are actually longer. The longest rib in both is the sixth. Struthers found, further, 

 that the degree of curvature is greater in the Humpback, thereby giving it a wider thoracic 

 cavity. 



The sternum is of characteristic form, thick and broad, with two lateral rounded wings, 

 and a short posterior portion. Its shape is subject to much individval variation, however. 



