. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. 300 CLASSIFICATION OF VERTEBRATES. this bone may be either freely movable or firmly united by suture to the adjacent bones, the first condition occurring only in snakes and lizards.^ The two rami of the lower jaw are usually united by ligament or by suture, but in turtles and pterodactyls the two are fused. Frequently vacuities occur in the jaw, and usually the component bones can be distinguished. In a few dinosaurs a predentary or mento-meckelian bone occurs at the symphysis of the lower jaw (Fig. 310).. Fig. 296. Sternum
. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. 300 CLASSIFICATION OF VERTEBRATES. this bone may be either freely movable or firmly united by suture to the adjacent bones, the first condition occurring only in snakes and lizards.^ The two rami of the lower jaw are usually united by ligament or by suture, but in turtles and pterodactyls the two are fused. Frequently vacuities occur in the jaw, and usually the component bones can be distinguished. In a few dinosaurs a predentary or mento-meckelian bone occurs at the symphysis of the lower jaw (Fig. 310).. Fig. 296. Sternum and shoulder girdle of lizard, Iguana, from Huxley, d, clavicle; cr, coracoid; ecr, epicoracoid; gl, glenoid fossa; id, episternum; mcr, mesocoracoid; msc, mesoscapula; sc, scapula; St, sternum; xst, xiphisternum. The hyoid and branchial arches are variously developed, but at no time have they gill-supporting functions. Frequently the first, or first and second, branchial arches are well developed, gi\'ing rise to long cornua attached to the well-developed copula. The pectoral girdle is developed in all reptiles — even the limbless lizards — with the exception of the ophidia Scapula, coracoid, and precoracoid are almost always present, the latter lacking in ichthyosaurs, plesiosaurs, and dinosaurs, while in 1 The fixed or free condition of the quadrate has heen employed in dividing the reptilia into monimostylica and 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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