NO. 5 TELESCOPING OF THE CETACEAN SKULL 4I 



It will be seen that this arrangement of the order does not differ 

 materially from those which have been most generally in use (for 

 a summary of the principal attempts at classifying the cetaceans see 

 W'inge, Smithsonian Misc. Coll., Vol. 72, No. 8, pp. 58-62) except in 

 the greater independence now attributed to all three of the suborders, 

 and, among the members of the Odontoceti, in the wide separation of 

 the ziphiids from the physeteroids, and especially in the separation 

 of the rather primitive iniids from Platanista, the genus which I 

 regard as presenting the greatest total of modifications known in any 

 cetacean. Aside from these admittedly controversial details the 

 departures from accepted usage, so far as such usage can be said 

 to exist, chiefly pertain to questions of judgment with regard to the 

 limits of the minor groups and the relative importance assigned to 

 some of these groups. That a classification based on a mostly untried 

 set of characters should coincide in the main with the classifications 

 already in existence indicates the general soundness of the broader 

 results of work on cetacean taxonomy. The differences in detail 

 are mostly the result of two causes : first, that some of the char- 

 acters hitherto regarded as indices to relationship now appear to 

 be parallel and independent modifications, and, second, that compara- 

 tively few of the extinct members of the order are known from re- 

 mains complete enough to show the features which are now seen 

 to be needed for a natural classification. Examples of the first are 

 furnished by the beak form supposed to bring together the other- 

 wise excessively different Platanista and Inia or Lipotcs; the tusk- 

 like tooth structure supposed to indicate relationship to the sperm 

 whales on the part of various fossil cetaceans known from teeth only 

 (this structure now appears to be merely a mechanical strengthening 

 of the teeth by means which have been independently adopted in the 

 sperm whale, the white whale and the ziphiids ; probably elsewhere 

 under the influence of appropriate stimulus) ; the unusual relation- 

 ship of the hindermost ribs to the vertebrae supposed to be evidence 

 in favor of placing the ziphiids in the same group with the sperm 

 whale notwithstanding the fundamental differences presented by the 

 structure of the skulls. Examples of the second are so numerous 

 that detailed listing is scarcely necessary in the present connection. 

 A few characteristic instances are furnished by the remains which 

 formed the bases of the following 30 generic names : Agriocetus, 

 Cetophis, Cetorliynchus, Delphinaviis, Delphinopsis, Dinoziphius, 

 Eucetiis, Hcspcrocctus, Hoplocetus, Iniopsis, IxacantJins, Kekenodon, 

 Metasqnalodon, Microcetus, Microseuglodon, Outocetus, Orycetero- 



