190 



THE SKULL. 



[chap. 



apex of the rostrum, embracing the mesethmoid cartilage, 

 and posteriorly reaches for a considerable distance beneath 



FMst 



Fig. 62. — Under surface of the cranium of a young Dolphin (Globicephalus melas), |. 

 BO basioccipital ; ExO exoccipital ; Per posterior (mastoid) process of periotic ; 

 Ty tympanic; Sg squamosal; AS alisphenoid ; OS orbitosphenoid ; ZM zygo- 

 matic process of malar ; Fr supraorbital process of frontal ; Ma body of malar ; 

 Pt pterygoid ; PI palatine ; Mx maxilla ; PMx premaxilla ; Vo vomer ; gf 

 glenoid fossa of squamosal ; tg deep groove on squamosal for meatus auditorius 

 externus, leading to tympanic cavity ; ^condj'lar foramen. 



the basisphenoid. It forms as usual the inner wall of the 

 posterior narial apertures. Behind these apertures the base 



