86 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



memoir. Most authors employ the term Tlatanistidae to include the two modern 

 subfamilies of Platanistinae and Iuiinae, together with the known fossil allies of 

 either. The arrangement proposed by Dr. Theodore Gill in 1872 differs from the 

 one commonly in vogue only in that the minor subdivisions are elevated to the 

 rank of independent families. At that time the Iniidae alone were known to have 

 fossil representatives, and even now opinion is divided as to which of the two 

 groups some of the fossil forms should be referred. Abel's scheme is practically 

 a revival of Gill's arrangement. In his latest memoir (1905) the family Platanis- 

 tidae is restricted to the genus Platanista itself. The Iniidae of Gill are renamed 

 Acrodelphidae, and made to comprise four subfamilies, one of which includes 

 Delphinapterus and Monodon. In addition, two other independent families are 

 recognized, one being typified by Eurhinodelphis, the other by Saurodelphis. All 

 of these family divisions are considered to have equal rank with the Physeteridae, 

 Ziphiidae, and Delphinidae, and to trace their origin back to Squalodon, but not 

 to Zeuglodon, which is regarded as much too highly specialized to have been the 

 direct ancestor of Squalodontidae. It is suggested that the latter were probably 

 descended from small terrestrial Carnivores, and the Delphinidae from still another 

 group, the Odontocetes being thus of diphyletic origin. Such, in brief, are Abel's 

 more general conclusions. 



In order to point out more clearly the exact equivalence between the so-called 

 Acrodelphidae of Abel, and the earlier defined Iniidae of Gill, we may be per- 

 mitted to reproduce the following summary given by the first-named author at 

 page 129 of his memoir on Odontocetes : — 



" Resume general : Par les caracteres de sa dentition et de son crane, Cyrtodel- 

 phis se montre etroitement allie a Argyrocetus, Inia, Pontistes et Pontoporia, 

 comme avec Acrodelphis, et doit done former un meme groupe avec ces formes. 

 Ce groupe correspondrait partiellement aux Platanistides, dans les limites que 

 Zittel a donnees a cette famille ; mais, comme Platanista doit etre elimine, il faut 

 choisir un autre nom. Puisque Acrodelphis est le type fossile le plus primitif de ce 

 groupe, on devra se servir du nom de famille Acrodelphidae. Nous aurons alors a 

 distinguer : 



"ACRODELPHIDAE. 



Argyrocetinae : Argyrocetus, Cyrtodelphis, Pontivaga, Ischyo- 



rhynchus, Champsodelphis. [s. str.] 

 Acrodelphinae : Acrodelphis, Heterodelphis 

 Iniinae : Inia, Pontistes, Pontoporia. 

 Beluginae : Beluga, Monodon." 



With regard to the last subfamily, which should properly be called Delphi nap- 

 terinae, the author makes the following observations : " Beluga et Monodon mon- 

 trent de grandes ressemblances avec les Acrodelphides, tandis qu'ils different des 

 Delphinides. J'ai, a cause de cela, considere ces deux genres comme une sous- 

 famille des Acrodelphides ; leur origine n'est pas encore e'claircie. Les vertebres 

 cervicales libres prouveut qu'ils ne descendent pas des Delphinides." 



