1899.] CRANIAL OSTEOLOGY OF THE PAKROTS. 27 



excavated, and the partition between the cavity and the quadrate 

 articulation is scarcely visible in the dry skull. The squamosal 

 and prootic articular surfaces are both wide, and are separated by 

 a deep groove, though in the quadrate bone itself there is but a 

 shallow groove between the two heads. The shaft of the quadrate 

 is longer and less massive than in the Cockatoos ; the quadrato- 

 jugal cup and the pterygoid condyle are both large ; the anterior 

 or orbital process is long and attenuated. The paroccipital wings 

 are largely developed, and run almost uninterruptedly below into 

 the basitemporal ridges. The posterior view of the skull is very 

 similar to that of Micror/lossa. On the dorsal border of the 

 foramen magnum can be detected U\o small articular facets : these 

 are produced by contact with the unusually developed spine of the 

 axis A'ertebra ; in Microghssa, on the other hand, t\AO small sub- 

 ordinate facets are present on either side of the occipital condyle. 



Fig. 18. 



Anadorhynchus hyaciiithiims (reducecl). 



In the Hyacinthine Macaw the anterior margin of the iuterorbital 

 septum is deeply notched, the lower portion running forward like 

 a curved and pointed blade. The anterior region of the cranium, 

 on either side of the upper portion of the septum, is hollowed out 

 into two immense and deep cavities, which are scarcely represented 

 in the other Macaws ; indeed, in this region, and on the corre- 

 sponding opposite face of the " prosopium," there are many in- 

 teresting characters to be recognized that lie beyond the scope of 

 this paper. The jugal bone is compressed from above downwards 

 at its anterior extremity, instead of from side to side as in 

 Microglossa. The angle of the mandible is obtusely truncated ; 

 the ramus presents no mandibular fontanelle ; the accessory 

 marginal articulation for the quadrate is large, elongate, and 

 connected by a smooth surface with the main articulation. 



Of the other Maca\^s, I have examined A. arnrcmna, cMoropiera 

 (fig. ]9, p. 28), macao, and maracana. That of A. arnrauna is 

 remarkable in having the orbital ring incomplete, though the long 



