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Show 1867.] PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. 459 5. The ALECTOROMORPHiE. The rostrum may be slender and depressed, or high and arched. Oval, flattened basipterygoid facets, sessile upon the basisphenoidal rostrum and articulating with corresponding surfaces upon the pterygoids, are always present. The maxillo-palatines are always lamellar, but vary greatly in size, being sometimes very small. The palatine bones are relatively long and narrow, with obsolete internal laminae, and rounded-off postero-external angles. The angle of the mandible is produced into a strong upcurved process. The sternum has either one or more, generally two, very deep posterior notches on each side ; when there are two, the external lateral processes thus marked out are much shorter than the internal. The feet vary considerably in the relative size and in the position of the hallux, and in the development of spurs. They are never completely, or even largely, webbed. The ratio of the phalanges of the front toes is as in the preceding groups. According to Nitzsch the feathers have aftershafts, and the pterylosis is remarkably uniform in all the genera except the Pteroclidce, a family which, in this and some other respects, but not in cranial characters, approaches the Pigeons. Except in Pterocles, the oil-gland is surmounted by a circlet of feathers. The inferior larynx is always devoid of intrinsic muscles. Excluding the Pigeons and the Tinamidce, this group corresponds with the Gallinae of authors, and contains the families Turnicidee, Phasianidce, Pteroclidce, Megapodidee, and Cracidee. The Turnicidee approach the Charadriomorphae, the Pteroclida; the Peristeromorphae ; while the Cracidee have relations with the birds of prey on the one hand, and with Palamedea and the other Chenomorphae on the other. 6. The PERISTEROMORPHCE. The rostrum is swollen at the tip, and provided at the base with a tumid membranous space, in which the nostrils open. The skull is provided with narrow, but prominent, basipterygoid facets. The maxillo-palatines are elongated and spongy. The angle of the mandible is not produced and recurved. The sternum has two posterior notches, the inner pair of which may be converted into foramina. The external lateral processes thus formed are, as in the Alectoromorphae, much shorter than the internal lateral processes. The hallux is on a level with the rest of the toes, and its metatarsal is peculiarly twisted. The anterior toes are not at all webbed. The ratio of the phalanges is as in the preceding groups. The feathers have no aftershaft (? Didus), and the oil-gland is devoid of a circlet of feathers. |