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Show 1899.] CRANIAL OSTEOLOGY OF THE PARROTS. 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 Microglossa. O n the dorsal border of the foramen magnum can be detected two small articular facets : these are produced by contact with the unusually developed spine of the axis vertebra ; in Microglossa, on the other hand, two small subordinate facets are present on either side of the occipital condyle. Fig. 18. Anadorhynchus hyaciuthinus (reduced). In the Hyacinthine Macaw the anterior margin of the interorbital 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 corresponding opposite face of the " prosopium," there are many interesting 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 bv a smooth surface w~ith the main articulation. Of the other Macaws, I have examined A. ararauna, chloroptera (fig. 19, p. 28), macao, and maracana. That of A. ararauna is remarkable in having the orbital ring incomplete, though the long |
