NO. 5 TELESCOPING OF THE CETACEAN SKULL 43 



by Koriig, Jahres-Ber. Mus. Franc. -Carol., Linz, Vol. 69, p. iii, 

 191 1.) Such details as can be seen are, however, in accord with the 

 conditions present in both the kind and stage of telescoping repre- 

 sented by Agorophiiis and Archcrodclphis. The reconstructions given 

 by Abel in plates 6 and 1 1 show, on the contrary, a structure which 

 differs fundamentally from that known to occur in any other cetacean. 

 The maxillar}- is represented as broadly united with the frontal by a 

 straight suture extending directly inward to the intermaxillary from 

 a point situated on the side of the rostrum in front of the anterior 

 margin of the orbit. No part of the maxillary extends behind this 

 level either above or below the frontal ; yet the intermaxillary runs 

 far back behind both maxillary and orbit, its extremity touching the 

 parietal. The fronto-maxillary suture, if correctly interpreted, is 

 not very different from that usually seen in the zeuglijdonts. The 

 relative degree of backward extension of the maxillary and inter- 

 maxillary is, on the contrary, something unknown either in zeu- 

 glodonts or in cetaceans wnth telescoped skulls. It should further be 

 noticed that essentially normal conditions, not very different from 

 those which appear to have been present in Agorophms were de- 

 scribed by Konig as occurring in the specimen afterward interpreted 

 by Abel. In the zeuglodonts the relationships of these tw^o bones have 

 remained normal, and the posterior border of the maxillary lies be- 

 hind the extremity of the intermaxillary (pi. 5, fig. i). During the 

 process of telescoping in all known cetaceans it appears to be the 

 maxillary which leads in the backward move, so that in rare instances 

 only does the intermaxillary attain the more posterior level, and then 

 by such a mere trifle as to form no real exception to the general 

 rule (see diagram of Rhachianectes, pi. 8, fig. 3). That the inter- 

 maxillary in any cetacean should have extended backward to the 

 parietal while the maxillary remained stationary in front of the orbit 

 is so contrary to probability that the evidence of an unusually well 

 preserved specimen would be necessary before anything of the kind 

 could be believed to have taken place. If such a condition should 

 ever be demonstrated to occur it would indicate the existence of a 

 third type of telescoping not directly related to or derivable from 

 either of those now known. That the genus Patriocetns as inter- 

 preted by Abel would be unlikely to represent a stage ancestral to the 

 modern baleen whales appears to be clearly enough indicated by the 

 character just mentioned ; it is made practically certain by the 

 absence of the orbital plate of the maxillary, no trace of which appears 

 either in Abel's photographs or restoration (based chiefly on the 



