| OCR Text |
Show 1895.] LORIUS FLAVOPALLIATUS AND PSITTACUS ERITHACUS. 387 The quadrate in P. erithacus 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 surface 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 tbe 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 the 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. flavopalliatus 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 absolutely, much smaller than in P. erithacus. 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. erithacus. In both it is decidedly convex transversely, but it presents a broadened-out gentle convexity in tbe latter species, while in the former (fig. 14, p. 390) it is narrower and sharper and therefore more convex. In 25* |
