PSITTACID^E.] OSTEOLOGIA AVIUM. [PSITTACIN.E. 



Order IV. PREHENSORES. 

 Fam. 1. PSITTACmE. 



Subfam. 1. Psittacin^e. 



Psittacus, Linn, 



Erythacus, Linn. 



Type of Prehensores, Psittacidse and Psittacinse. 



Cranium gradually arched from the base of the nasal bones to the occiput, without 

 any central longitudinal depression ; occipital ridge and protuberance slightly marked. 

 Orbits well defined ; the antorbital processes bounding them anteriorly with the points 

 curved backwards. Septum perfect, except where perforated by the optic nerves. 

 Nasal orifices of moderate size, rounded ; a moderate transverse depression at the base of 

 the bill. Palatine bones placed vertically, except at their anterior extremities, which 

 are horizontally flattened, and expanding gradually for their anterior half; the hinder 

 exterior angles projecting backwards, and armed near their extremities with a strong 

 spine, from which the posterior margin slopes gradually upwards and forwards to the 

 junction of the interarticular bones. Interior margins united by a ligament posteriorly, 

 anteriorly diverging and terminating with a blunt spine ; a blunt, but somewhat 

 lengthened spine, pointing backwards, arises on their inferior surface just below the 

 junction of the interarticular bones ; zygomatic bones very long, articulated with the 

 ossa quadrata and the maxillaries, which, with the nasal bones, are not anchylosed to the 

 frontal bone, but have an elastic ligament between them, thus allowing a considerable 

 upward motion to the upper jaw. Sphenoid without any transverse or basilar portion. 

 Foramen magnum large, its inferior margin straight, the lateral margins gradually arched 

 upwards, placed somewhat obliquely. Inferior maxillaries very broad and strong, broadest 

 at about one-third of their anterior length ; posteriorly with the superior edges rising 

 much above their articulations with the ossa quadrata ; posterior end sloped from the 

 articulation downwards and backwards to a point. 



Sternum of nearly the same breadth posteriorly as anteriorly, the lateral edges con- 

 stricted just behind the junction of the ribs ; posterior margin rounded, and having a 

 somewhat oval foramen on each side; keel very broad, continued to the posterior margin 

 of the sternum, the inferior edge very slightly arched, the anterior point very much 

 rounded ; the anterior edge slightly excavated below the manubrial process, which is 

 bifid at its extremity. 

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