CHAPTER VII. 



THE RORQUALS 

 FAMILY, BALsENOPTERIDAE 



THIS family may be distinguished from that of 

 the Balaenidae by the following definition : 



Head less than quarter of the length of the body. 

 Dorsal fin usually present. Throat with longitudinal 

 plaits more or fewer in number. Bones of skull but 

 slightly arched. Tympanic bones more elongated. 

 Coronoid process of mandible more or less developed. 

 Cervical vertebrse usually free. Hand narrow and 

 tetradactylous. Baleen plates short. Caecum present.* 



This family of whales comprises at least three 

 well - marked genera : the Rorquals, genus Balcen- 

 optera ; the Humpbacks, genus Megaptera ; and 

 finally the recently - known California Grey whale, 

 Rhachianectes. f We shall commence with a con- 

 sideration of the Rorquals, which will be here 

 included within a single genus. This is probably 



* The above classification and definitions are chiefly founded upon 

 Sir W. Flower's paper in Proc. Zool. Soc. for 1864, p. 384. 



t Whether Professor Giglioli's Ainphiptera pacifica with two dorsal 

 fins (see p. 14) is an abnormality or not remains to be seen. (Cetacea 

 of the " Magenta?} 



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