xii.] CETACEA. 213 



vertical, they are not straight, but curve round the anterior 

 end of the brain cavity, both upper and lower orifices (an and 

 /) being directed somewhat backwards. They are com- 

 pressed from before backwards above, but wider and more 

 round below. The nasal bones (No), instead of being 

 lamelliform and roofing over the nasal passages, are reduced 

 to nodular masses, lying in depressions in the frontals, but 

 forming as usual the hinder boundary of the anterior narial 

 openings. 



In front of these openings, the face stretches out into 

 an elongated, depressed, pointed beak, or rostrum, formed 

 by the premaxillae and maxillae surrounding the vomer and 

 mesethmoid cartilage. The premaxillae send prolongations 

 upwards to form the lateral boundaries of the narial orifice, 

 and it is remarkable that these are not quite symmetrical, 

 that of the left side being the shortest. The orifice itself, 

 moreover, is rather inclined towards the left. Between the 

 antorbital process of the maxilla and its rostral prolongation 

 is a deep notch, the "antorbital notch." The upper surface 

 of the face, near this notch, has several very large foramina 

 for the transmission of branches of the fifth nerve. 



The elongated, pointed, and convex palate is formed 

 chiefly by the maxillae (Mx), the premaxillae (PMx) only 

 appearing for a short space near the apex. Behind the 

 maxillae, the palatines (PI) are somewhat wide laterally, 

 but towards the middle line form an exceedingly narrow 

 strip, inserted between the maxillae and the pterygoids (Pt) ; 

 the latter are greatly developed ; besides forming the outer 

 wall of the posterior nares, each sends a lamella inwards, 

 which nearly (in most Dolphins, completely) meets its fellow 

 in the middle line, and so prolongs the bony palate back- 

 wards. This process, moreover, is reflected outwards again 

 from its inner or lower edge, and, joining with a projecting 



