388 TRUE— ON THE CLASSIFICATION OF THE CETACEA. [April 24 



I think that we shall in the end come to agree with the opinion 

 expressed many years ago by Dr. Theo. Gill,'' that the origin of the 

 Cetacea dates much further back than is generally believed, and that 

 the forms above mentioned are sideshoots from a stem reaching into 

 a much more remote past. 



However it may be as to the origin of the families mentioned, 

 Professor Abel is correct, I believe, in following the course of Gray'^ 

 and GilP in separating the sperm whales and the beaked whales into 

 two families, the Physeteridse and the Ziphiidje. Abel's line of de- 

 velopment for Physcter through Scaldicetus, Physeteruia, Prophy- 

 scter and Placoziphius seems excellent, except that it ignores Hypo- 

 cetns Lydek. (or DiapJiorocetiis Amegh.) of North and South 

 America, which is certainly an ancestor of Physeter or Kogia, and 

 probably the former. 



The family EurinodelphidcC of Abel is quite certainly distinct. 

 While obviously allied to the Ziphiidse, Eurinodclphis has distinc- 

 tive characters of its own, such as the small pterygoids, very long 

 toothless premaxillse, a delphinoid prenarial region, etc. I suc- 

 ceeded in discovering a skull of this genus in the Miocene of Mary- 

 land last year and thus introducing the family into the American 

 fauna. 



Abel's family Acrodelphidc-e, which, as Professor Eastman re- 

 cently pointed out, should be called Iniidse'', while not entirely new, 

 is a very interesting assemblage. It comprises the following sub- 

 families and genera : 



Family Iniid.e Gill (Acrodelphid^ Abel). 



Argyrocetiis. 



Argyrocetinse 



Acrodelphinas 



Cyrtodelphis. 

 Pontivaga. 

 Ischyorhynchus. 

 Champsodelphis. 



r Acrodelphis. 

 I Heterodelphis. 



"Amer. Nat., 7, 1873, p. 2. 



'Cat. Seals and Whales Brit. Mus., 2d ed., 1866, p. 326. 



* Smithsonian Misc. Coll., 11, 1872, p. 15. 



^ Bull. Mus. Comp. Zool., 51, 1907, p. 86. 



