1895.] LOKIUS PLATOPALLIATUS AND PSITTACU8 EEITHAC0S. 387 



The quadrate in P. enthacus has its columnar process long and 

 stout. At its apex is a large external and smaller internal articular 

 surface separated by a narrow groove. 



Its orbital process is short, delicate, and pointed (see fig. 2, 

 p. 364), arching forwards and inwards just above the pterygoid. 

 A short but deep concavity separates it from the anterior end of 

 the inferior surface of the quadrate, which there projects forwards, 

 developing a small rounded condyle (separated slightly from the 

 anterior end of the long articular surface, or elongated condyle for 

 the mandible) which fits into cup of hinder end of pterygoid. 



The zygomatic process presents ventrad an outer articular sur- 

 face in the form of an antero-posterior convexity and a slight 

 transverse concavity to articulate with the mandible dorso-laterally. 

 This is the part of the quadrate which articulates with the upper 

 articular surface of the mandible, while the elongated ventral 

 condyle of the quadrate articulates with the long concave inferior 

 articular surface of the mandible. The inferior articular surface 

 of the quadrate is elongated and nearly straight (slightly concave 

 mesiad), extending forwards and inwards on a line with the 

 pterygoid which is in front of it. Above it is the little condyle 

 for tbe cup of the pterygoid above-mentioned. In both species the 

 elongated condyle for the mandible is larger at its anterior end, 

 but more predominantly so in P. erithacus. Just above its anterior 

 end is the articular convex surface for the pterygoid, while in 

 front of the apex of the zygomatic process is a small cup to receive 

 within it the end of the zygoma. 



The extent of the body of the quadrate behind the zygomatic 

 process is longer than that in front of it to the front margin of 

 the base of the ascending orbital process, and the depth from the 

 zygomatic process about equals the length thence to the apex of 

 the orbital process. In both species the hinder margin of the 

 quadrate is continuous and does not develop any strongly projecting 

 process. 



In L. JlavopalUatus the ascending columnar process is relatively 

 longer and more slender. The extent of the quadrate behind the 

 zygomatic process is also shorter than that in front of it to the 

 front margin of the base of the orbital process, and its depth from 

 the apex of the zygomatic process is shorter than from that point 

 to the apex of the orbital process, — the inferior and still more the 

 hinder portion of the quadrate being, relatively as well as abso- 

 lutely, much smaller than in P. e7-ithacus. 



III. The Mandible. 



The symphysial portion of the dentary part of the mandible 

 externally, is nearly straight antero-posteriorly (i. e. dorso-ventrally) 

 in L. flavopalliatus but gently convex in P. enthacus. In both it 

 is decidedly convex transversely, but it presents a broadened-out 

 gentle convexity in the latter species, while in the former (fig. 14, 

 p. 390) it is narrower and sharper and therefore more convex. In 



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