TOOTHED WHALES 173 



whale) on the left side, may be mentioned. The ribs 

 have always either bony or cartilaginous sternal 

 moieties, which articulate with the usually composite 

 sternum. A fair number, moreover, thus articulate. 

 The ribs too, more or fewer of them, have both a 

 capitular and a tubercular head, articulating respect- 

 ively with the transverse processes and with the 

 centrum of the vertebrae. 



The two rami of the mandible unite by a longer or 

 shorter, but always definite, symphysis, not a mere 

 fibrous union such as is met with in the whalebone 

 whales. 



So sharply defined are the Odontoceti from the 

 Mystacoceti that intermediate types are sadly to seek ; 

 and both divisions, in fact, have each specialised on 

 their account in the same kind of direction in parallel 

 lines. We have great-headed Cetaceans in both 

 groups. The Cachalot corresponds to the Right 

 whale. There are giants and pigmies among the 

 families of each. The small Kogia is a near ally of 

 the bulky Cachalot. The somewhat dwarfish Neo- 

 balcena is not far off from the leviathan of the Green- 

 land seas. There are Odontocetes without a dorsal 

 fin, and Odontocetes with that fin. The Rorquals 

 correspond to the latter, the Greenland whale to the 

 former. The pectoral fin is large in Megaptera and 

 Globicephalus, small in Neobalcena and Physeter. 

 The throat is grooved for extensile purposes in 

 Balaenopteridae and in the Ziphiidae. All these are 

 parallelisms, and not evidence of affinity. So, at 

 least, it seems to us. 



