202 , THE SKULL. [chap. 



approached in some of the Dolphins. In the floor of the 

 great narial opening is seen the vomer ( Vo), of very delicate 

 structure, and posteriorly the ossified portion of the mes- 

 ethmoid (ME) of considerable vertical extent. The olfac- 

 tory chamber of the nasal cavity is greatly compressed from 

 side to side, and contains a series of simple, longitudinally 

 placed ethmoturbinals, of which the upper one is very 

 much the largest. There are no maxilloturbinals in any 

 skulls which I have examined. 



In front of the narial opening the face is prolonged into 

 a narrow rostrum, formed by the premaxillae, supported 

 below and at the sides by the maxillae. The under 

 surface of this is very rugose, and in life supports a horny 

 plate. There is a large, oval, single, median anterior palatine 

 foramen. The palate is long and narrow between the two 

 parallel rows of numerous molar teeth. It does not extend 

 beyond the last of these, and is formed almost entirely by 

 the maxillae, the horizontal plates of the palate bones 

 being very narrow. Behind each row of teeth is a massive 

 descending rough process, formed by the union of the 

 palatine, pterygoid plate of the alisphenoid, and true 

 pterygoid. Posteriorly this has a longitudinal groove 

 corresponding to the pterygoid fossa. Behind these the base 

 of the skull contracts in width, leaving a large opening on 

 each side of the basioccipital, between the alisphenoid in 

 front and the exoccipital behind, and only partially filled by 

 the tympanic and periotic. 



The two last-named bones are ankylosed together, but not 

 to any of the other bones of the skull, and though freely 

 moveable in the dried skull, they are retained in their place 

 by the overhanging process of the squamosal. 



The tympanic (Ty) consists of a large and very solid half- 

 ring, with its lower margin considerably thickened and 



