HISTORY OF WHALES 



7i 



glauconiferous clay in the province of 

 Siena, Italy, and seems to be a true 

 Tar si ops. 



The living killer whale, Orcinus orca, 

 seems to have descended from the same 

 stock as Tursiops, and it is not unlikely 

 that some of the confusion that exists 

 as to the relationships of some of the 

 Pliocene porpoises is caused by resemb- 

 lances due to this common origin. In 

 any event, an extinct killer whale Orcinus 

 citoniensis (Capellini, 1883) occurs in the 

 Middle Pliocene of Italy. A nearly com- 

 plete skeleton, skull, and mandibles of 

 this porpoise was found at Cetona in 

 Tuscany. It has 14 teeth in each jaw, 

 while the living killer whale has from 

 10 to 14. 



In a similar manner, we may trace back 

 the ancestry of the living porpoise Steno 

 with a moderately long rostrum to the 

 Middle Pliocene Steno bellardii (Portis, 

 1885) found near Asti, Italy, and the 

 Lower Pliocene Steno gastaldii (Brandt, 

 1874) from the Piemonte district of 

 Italy. 



Slender-snouted porpoises belonging to 

 the subfamily Stenodelphininae differ 

 from those referred to the Delphininae by 

 having pterygoids with large reduplica- 

 tions, which overspread the corresponding 

 alisphenoid, and separate cervical verte- 

 brae. The telescoping of the skull has 

 proceeded along the same lines as in the 

 Delphininae. It is fairly certain that 

 their geological history dates back into 

 the Miocene, and that they represent a 

 line of descent that has paralleled the 

 long-snouted porpoises of the Miocene. 

 Their remains have not been recognized as 

 yet in the Miocene formations, and it is 

 not until the Lower Pliocene that we are 



aware of their presence in former pelagic 

 faunas. 



Pontistes rectifrons (Burmeister, 1885) is 

 represented solely by a cranium, lacking 

 the distal portion of the rostrum and the 

 teeth, but otherwise quite complete, 

 found in the Lower Pliocene marine 

 deposits on the bank of the Parana River 

 near the town of Parana, Argentine 

 Republic. The skull shows a striking 

 resemblance to the living Stenodelphis, 

 but is twice as large in all its dimensions. 

 It agrees with Stenodelphis in the squared 

 occipital region, elevation of the pre- 

 maxillaries in front of the narial passages, 

 rather slender and somewhat pointed 

 zygomatic processes placed far forward, 

 and slender rostrum. The main differen- 

 ces as far as regards the superior aspect 

 of the skull are that in Stenodelphis there 

 is a more obvious side to side constriction 

 of the interorbital region and the lateral 

 margins of the maxillaries are turned 

 upward above the orbits. Furthermore 

 the teeth are about one-third as large and 

 are more closely approximated. A small 

 fragment of the rostrum of a Pleistocene 

 porpoise recently found at San Diego, 

 California, shows so close a resemblance 

 to Stenodelphis that it tends to confirm the 

 former existence on the Pacific Coast of a 

 member of the subfamily Stenodelphin- 

 inae. The teeth of Stenodelphis sternbergi 

 (Gregory and Kellogg, 19x7) have the 

 same peculiar shape as those of Steno- 

 delphis, having an axe-like root and a 

 slender crown, but are less closely spaced. 

 The living member of this subfamily, 

 Stenodelphis blainvillei, survives in some 

 of the fresh water streams of Argentina, 

 Uruguay, and Brazil. 



(To be concluded) 



