306 A BOOK OF -WHALES 



two genera assigned by Cope* to the Platanistids 

 which approach Zeuglodon in one point, and that is 

 in the length of the cervical vertebrae ; these are 

 Zarrhachis and Priscodelphinus. This character, 

 however, as it seems to us, is rather one that betokens 

 antiquity than one which points in any particular 

 direction. The general tendency of whales of every 

 group to lose their teeth is exhibited in these old 

 Platanistidae ; the genus Rhabdosteus has teeth at the 

 base of the maxillary only ; in Agabelus the teeth 

 seem to have entirely vanished, leaving only an 

 alveolar groove, which may, perhaps, have contained 

 rudimentary teeth like those now found in the upper 

 jaw of Physeter and the Ziphioids. Some other facts 

 dealing with fossil members of this group will be 

 found at p. 209. 



* "The Cetacea," American Naturalist, 1890, p. 599. 



