FOSSIL TOOTHED WHALES 209 



point is that some of the upper jaw teeth are im- 

 planted in the pre-maxillse. The total length of the 

 skull is about 10 feet, so that it falls short of that of 

 the Sperm whale. 



Argyrocetus pat agonic us is mainly known from a 

 skull. This shows that the animals were about as 

 big as the dolphin genus Steno. It shows several 

 archaic characters. In the first place the occipital 

 condyles, whereon articulates the first vertebra, are 

 in shape more like those of terrestrial mammals in- 

 stead of being adpressed to the skull, as in the 

 Cetacea generally. The nasal bones too are large 

 and well developed ; the rostrum is long and slender ; 

 the skull generally is bilaterally symmetrical. It has 

 been pointed out by Mr. Lydekker* that the fossse 

 upon the maxillary bones are squared and flattened 

 like those of Pontoporia. As in the Platanistids, 

 moreover, the cervical vertebrae, or at any rate 

 cervicals found in association with the skull, are 

 all free, and longer than is the rule among more 

 modified Cetacea. The end of the mandible is up- 

 turned, smooth, and without teeth, and is unlike that 

 of any existing Cetacean. 



* Ann. Mus de la Plata, 1893. 



