26 PBOF. d'aeCY W. THOMPSON ON THE [Jau. 17, 



well-marked. The quadrate articulation is scarcely separated in 

 the dry skull from the tympanic cavity. The " suprameatal area " 

 is rather large and faces outwards ; it is in fact unusuallv con- 

 spicuous, though vastly less developed tlian in Nestor. The inner 

 head of the quadrate is small, widely separate from the outer, and 

 bent sharply inwards ; the pterygoid condyle is imperfectly separate 

 from the mandibular. In the mandible the marginal surface of 

 articulation with the body of the quadrate is very conspicuous, 

 and the edge of the mandible is here bent outwards. A small 

 mandibular foutanelle is present ; the angle of the jaw is short 

 but pointed. As in Cockatoos generally, the interorbital vacuity 

 is small and rounded. In one point, not among those chiefly con- 

 sidered in this paper, the skull of Cahpsittacus differs from its 

 congeners: between the anterior rami of the palatines there are 

 visible (as in Psittacus) two long processes descending from the 

 posterior portion of the maxillary bones ; these are the " median 

 processes of the inferior margin of the postaxial surface of the 

 prosopium," in Dr. Mivart's description of Psittacus. They are, 

 as a rule, small or obsolete in the other Cacatuidse. It is clear 

 that the skull of Cahpsittacus, though at first sight very similar 

 to, is different in several respects from, the true Cacatuine type. 

 It is possible that these differences involve resemblances to the 

 Platycercini, and this question will be further discussed below. 



Family Nasiternix^. 



I have examined the tiny skull of N.pygmcea in an example 

 unfortunately not full-grown, belonging to the Museum of the 

 E. College of Surgeons. It is impossible to rest much weight on 

 this beautiful but imperfect little skull. The orbit is exceedingly 

 incomplete, the prefrontal process being very short (the prefrontal 

 bone IS not yet quite co-ossitied with the frontal, and is in close 

 connection for an almost equal extent of contact with the nasal). 

 The postfrontal proc-ess is also small and scarcely prominent ; the 

 squamosal process, on the other hand, is long and slender and 

 directed obliquely downwards. The posterior border of the 

 auditory meatus is nearly straight. The suprameatal tubercle 

 and its subjacent groove are both well marked. 



The Macaws. 



The great Blue Macaws differ, as is well known, from the rest 

 in certain of their cranial characters. In Anaclorh/nohus hijacin- 

 thinus (tig. 18, p. 27) the orbit is incomplete, the prefrontal process 

 terminating in a sharp point below the middle of the orbit. The 

 postfrontal process is of moderate size, short but massive ; the 

 squamosal process is rather small, and united nearly to its tip on 

 the inner side by a bridge of bone to the edge of the temporal fossa. 

 The auditory meatus is wideandapproximately square in outline; the 

 posterior and superior recesses of the tympanic cavity are scarcely 



