ORDER CETACEA. 



1303 



the Right Whales of the Southern Seas. Paltzocetus, which has been 

 regarded by its describer as of Mesozoic age, may be provisionally 

 referred to this section ; the type was probably obtained from the 

 Red Crag. In the Balcenopterine section a dorsal fin is very gene- 

 rally present (whence the name " Finners " applied to many of these 



Fig. 1173. — Left lateral view of the skull of the Greenland Whale (Balczna mystacetus). 

 Greatly reduced. (After Owen.) 



Whales) ; the cervical vertebrae are free, and thicker than in the 

 Balce?ii?ie section; and the tympanic (fig. 11 74) is longer, more in- 

 flated, and more rounded than in the latter. The existing genus 

 Megaptera (in which may be included the fossil Burtinopsis) is 

 abundantly represented in the Pliocene Crags of both England and 

 Belgium. Balce?ioptera also occurs commonly in the same deposits ; 

 B. defi?iita being apparently nearly allied to the existing B. sibbald\ 



Fig. 1174. — Inner view of the right tympanic of a Rorqual (Balcenoptera muscidus). 

 Recent. One-half natural size. (After Gray.) 



which attains a length of 80 feet ; while B. e??iargi?iata comes nearer 

 to the living B. rostrata, which is seldom more than 30 feet in length, 

 Cetotherium (including Cetotheriophanes, Plesiocetus, and Plesiocet- 

 opsis) is characterised by the narrowing of the anterior extremity of 

 the tympanic, and is likewise found in the Crags and other Pliocene 

 vol. 11. 2 D 



