. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. BIRDS. 337 All existing birds are toothless, but the dental ridge (p. 19) is formed in the embryo of at least a few forms. In several fossil birds teeth were present, either in grooves (^ArchcBopteryx,. Fig. 331. Pelvis of Apteryx, after Marsh, from Wiedersheim. a, ace- tabulum; //.ilium; m, ischium; /i, postpubis; /, prepubis. Hesperornis) or in alveoli (Jchthyornis). Many modern birds have the horny sheath of the beak produced into horny tooth-like processes, which in many cases are supported by corresponding elevations of
. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. BIRDS. 337 All existing birds are toothless, but the dental ridge (p. 19) is formed in the embryo of at least a few forms. In several fossil birds teeth were present, either in grooves (^ArchcBopteryx,. Fig. 331. Pelvis of Apteryx, after Marsh, from Wiedersheim. a, ace- tabulum; //.ilium; m, ischium; /i, postpubis; /, prepubis. Hesperornis) or in alveoli (Jchthyornis). Many modern birds have the horny sheath of the beak produced into horny tooth-like processes, which in many cases are supported by corresponding elevations of the bone. The tongue is well developed and protrusible, and exhibits many modifications in form. In most birds the oesophagus is of the same size throughout, but in grain-eating birds and birds of prey it has an enlargement or crop which serves as a reservoir of food, and in many cases is glandular, and hence plays a part in digestion. The stom- ach always consists of two divisions, an anterior glandular stomach or proventriculus and a second muscu- lar stomach or gizzard, the muscles of the latter, which radiate from a tendinous centre on either side, being best devel- oped in the grain-eating forms. A ' pyloric stomach' occurs. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Kingsley, J. S. (John Sterling), 1854-1929. New York, H. Holt and Company
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