68 



BULLETIN 73, UNITED STATES NATIONAL MUSEUM. 



SKULL. 



The skull of Berardius bairdii presents many characters by which it may be 

 distinguished from that of arnuxii, whether adult or young. As compared with 

 the latter, the rostrum is less massive at the base. The pterygoid has a rounded 

 extension posterior^ and superiorly, so that the posterior portion of the upper 

 border of the pterygoid sinus is convex, rather than nearly straight, as in arnuxii. 

 The exoccipital is larger and broader distally below, and its external surface is 

 plane or concave, rather than convex, as in arnuxii. The distal end of the zygo- 

 matic process is much more incurved. The nasal bones instead of presenting 

 lateral extensions have nearly straight sides. The vomer is deeply emarginate at 

 the base of the skull posteriorly where it rests against the presphenoid. The pala- 

 tines extend scarcel}^ or not at all in front of the pterygoids. The foregoing differ- 

 ences will readily be seen by comparing the figures on Pis. '26-29 with those of the 

 type of B. arnuxii given in Van Beneden and Gervais's Osteography, plate 23. 



The following are dimensions of skulls of both species: 



Dimensions of Jive skulls of Berardius bairdii {including the type) and of three skulls ofB. arnuxii. 



" From Van Beneden and Gervais figure. 

 SA little broken at tip. 



c" Suprafrontal processes of maxillae." 

 d Same point. 



