HUMPBACK WHALE. 291 



Description. 



Form. — The body is rather short and robust in comparison with the Fin Whales, and 

 the peduncle too seems shorter in proportion. The throat folds, extending from the lower 

 margin of the jaws back to the region of the navel, are fewer and much farther apart than in 

 the genus Balaenoptera. In three Newfoundland specimens, True found the number of these 

 folds to be 14, 20, and 22 respectively between the pectoral fins, and the widest were from 5 

 to 8 inches. A fold or two is present at the corner of the mouth, passing to the pectoral, back 

 of which may be two or three short transverse furrows. As in the Fin Whales, the folds on 

 the throat anastomose in some degree. Thus a fold from the lip may unite with a second or 

 it may itself bifurcate, forming two; others run continuously from the lower margin of the 

 ramus to the abdomen. The most median folds do not end at the point of the jaw but a slight 

 distance back from it, forming there a slight eminence or "chin" (as Struthers puts it). 



A characteristic of the Humpback is a series of dermal tubercles on the rostrum and jaws 

 (True's plate, 1904, Plate 41, shows them well). There is much variation in the number 

 of these, but on the snout they are arranged in three rows: a median row of usually about 

 five to seven extending from the blowholes to the snout, and a lateral row of from eight to 

 thirteen on each margin of the upper jaw, commencing slightly in advance of the angle of the 

 mouth. On the lower jaw is a distinct group of tubercles on each side of the symphysis, and 

 an irregular series of a dozen or more along the side of each mandible, often in a more or less 

 double series. 



The blowholes are situated on a slight eminence at the vertex of the head. In shape they 

 are a Uttle convex toward each other and converge anteriorly. There is a median linear de- 

 pression about an inch deep between them. 



In a specimen hauled ashore and resting on its belly, there is seen to be a distinct depres- 

 sion at the neck. 



The pectoral fin is of extraordinary length and flexibihty. It is longer than that of any 

 other whale, from 30 to 36% of the total length. The anterior outline is gently convex, with 

 a recurved tip; the posterior margin is similar, becoming concave at the tip. The anterior 

 margin has a series of eight prominent knobs, corresponding to the carpal joint and the joints 

 of the phalanges of the short first and long second bony fingers. The knobs corresponding 

 to the base and the tip of the first finger of the skeleton are largest. Between them are two 

 smaller knobs, and distal to the second big knob, are the four remaining. There are a few 

 smaller protuberances at the tip on the posterior margin as well. 



The dorsal fin of the Humpback, though subject to considerable variation in shape and 

 size, is in reality not very different in form from that of the Finbacks, though commonly rather 

 less falcate, more ridge-like, and truncate posteriorly, not like a hump as might be thought. 



