CLASSIFICATION, AND PHTLOGENY OF THE DIXOENITHID.E. 395 



In Meso2)tertjx, species /3 (Plate LX. fig. 21) there are distinct paired vomers ; a similar 

 condition appears to obtain in Anomalopteryx and in young skulls of Emeus crassus. 

 Owen's figure of Dinorms torosus (20, pi. 15 ; Ext. Birds of N. Z. pi. 82) also shows 

 paired vomers ; probably their concrescence is a sign of age. 



The palatine is a delicate, twisted plate of bone, passing from the anterior end of the 

 maxilla in front to tlie pterygoid behind (fig. 6). Its anterior end is somewhat fan- 

 shaped and underlaps the maxillo-palatine ; immediately posterior to this expanded 

 portion it is notched for articulation with the recurrent process of the maxilla. The 

 whole bone is twisted, the inner border of its anterior end becoming ventral in the 

 middle and finally external at the posterior end ; at the same time the dorsal border 

 turns mesiad, reaching to within a short distance of the rostrum. The posterior end 

 is obliquely truncated and articulated by all but its ventral extremity with the vomer, 

 becoming ankylosed with it in the adult. Tlie ventral extremity of the posterior 

 border is produced into a thickened squarish vomerine process (vo.pr.) which underlies 

 the posterior end of the vomer, and laterad of this process the bone presents a 

 short pointed end which underlies the pterygoid. 



The i)terygoicl {pt.) is a stout irregular bone with a bluntly-pointed anterior and a 

 thickened posterior end. By about the anterior half of its ventral border it articulates 

 with the combined palatine and vomer ; by its inner surface it articulates with the 

 basi pterygoid process ; its outer surface lies parallel to and in close contact with the 

 orbital process of the quadrate ; and its posterior end expands into a somewhat pedate 

 surface for articulation with the quadrate. 



e. The Quadrate. 



The quadrate consists, as usual, of a hody bearing the condyle for articulation with 

 the mandible, an upwardly-directed otic process, terminating in the head for articu- 

 lation with the tympanic cavity, and a forwardly-directed orbital pirocess. 



The articular surface on the head is somewhat wider at its outer than at its inner 

 end, and presents no trace of the double facet found in Apteryx. The otic process is 

 subtrihedral, presenting a lateral larder running upwards from the quadrato-jugal 

 facet, a mesial border from the outer condyle, and an anterior border from the orbital 

 process ; a posterior surface between the mesial and lateral borders, a mesial surface 

 between the anterior and mesial borders, and a lateral surface between the anterior 

 and lateral borders. On the mesial surface, just where the otic process merges into 

 the body of the bone, is a pneumatic foramen which varies greatly in size in the 

 different species and even in different individuals of the same species ; speaking gener- 

 ally, it appears to be large in Binornis, Anomalopteryx, and Pachyornis as well as in 

 Mesopteryx, species /3 ; smaller in Emeus, and smallest of all in Mesopteryx casuarina. 

 In Anomalopteryx didiformis there is sometimes a second pneumatic foramen on the 



