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



6. The new family Saurodelphidse. 



7. The family Platanistidse, consisting of Platanista only. 



The zeuglodonts are included in the order Cetacea by the ma- 

 jority of cetologists, though they were rejected from the great 

 " Osteography " of Van Beneden and Gervais, as these authors did 

 not consider them to be cetaceans. Brandt placed them with the 

 squalodonts as families in a tribe subordinate to the Odontoceti,- but 

 nearly all other authorities have considered them as a distinct sub- 

 order, — Archaeoceti, or Zeuglodontes. 



It seems to be generally agreed that the zeuglodonts have been 

 proven by the researches of Dawes, Fraas, Stromer, Andrews and 

 others to be derived from the creodonts. I do not know from what 

 particular creodont they are supposed to have sprung, and whether 

 the connection is good in that direction is for those most familiar 

 with the creodonts to decide. The chief argument appears to be 

 that in some zeuglodonts some of the molars are three-rooted. 



Whatever may be the truth as regards that connection, various 

 , zoologists have proposed, in more or less definite terms, to unite the 

 zeuglodonts to the ordinary cetaceans through the squalodonts,. 

 which are clearly cetaceans, but with two-rooted or three-rooted 

 teeth having serrated crowns. Professor Abel advances the con- 

 crete proposition of uniting the zeuglodonts and squalodonts^ 

 through the small form from the Caucasus, described by Lydekker 

 under the name of Zcuglodon caiicasicus,'^ and afterward made the 

 basis of a new genus, Microseuglodon, by Von Stromer. Of this 

 only a part of the lower jaw, the humerus and a caudal veViebra, are 

 known. The upward turn of the superior margin of the jaw pos- 

 teriorly, and the form of the humerus — particularly the quite good 

 articular facets, — appear to me to indicate that this is a zeuglodont, 

 with no very strong leaning toward Sqiialodon. If this be con- 

 ceded, there is no way at present in which to connect the Cetacea 

 with any group of land mammals. 



I would point out in this connection that while Microzeuglodon 

 is from the Eocene and is of small size, and Sqiialodon is from the 



^ Mem. Acad. Imp. Sci. St. Petersburg, VIP Serie, XX, 1873, p. vii. 



*L. c, p. 34- 



*Proc. Zool. Soc. London, 1892, p. 558, pi. 36. 



