BLUE WHALE. 



251 



grooves have not yet formed, but the muscle just described will eventually become the elastic, 

 plaited bag of the throat. 



Skeleton. — The skeletal characters of the Blue Whale are still imperfectly known, and of 

 American specimens there are very few measurements published. These relate chiefly to a 

 New Jersey skeleton preserved in the Philadelphia Academy of Sciences. It will suffice to 

 summarize the chief points that distinguish this species from the Common Finback. 



The most obvious peculiarity of the skull is the relatively greater breadth of the rostrum, 

 which, instead of being narrow and tapering is proportionally broader than in the Common 

 Finback with convex outUnes (Plate 11, fig. 3). Thus in the latter species the average breadth 

 of the rostrum at the middle is about 19.6% of the length of the skuU (True) while in the Blue 

 Whale the breadth at this point is nearer 29%. The palatal bones are also broader, and the 

 nasals are truncate across at their anterior end. In other respects the skull is much like that 

 of the Common Finback. The principal dimensions of the New Jersey skull are given by 

 True as follows : — 



Except for this specimen, no skull measurements of the Blue Whale are available for American 

 waters. 



The number of vertebrae is nearly the same as for the Common Finback, but the number 

 of caudals is usually one or two more. Three foetuses dissected with care by Dr. True (1904, 

 p. 182) at Newfoundland .showed the following variation: 



These counts express about the usual variation and accord fairly with those published 

 for adult European examples. The number of ribs is usually fifteen but occasionally is 

 sixteen, and so few as fourteen are recorded in one case. The lumbars are from thirteen to 

 sixteen, commonly fifteen, the caudals from twenty-six to twenty-eight. The total number of 



