. Outlines of zoology. ls General Characters.— TheCrocodilians are carnivorousfresh-water reptiles of large size,now represented by a few genera, Crocodilus, Alligator, andGavialis. The skin bears epidermic scales,underneath some of which thereare dermic bones or scutes. The tail is laterally compressed,and assists in swimming. Teeth occur in distinct socketsin the premaxillce, maxillce, anddentaries. In modern Crocodilians, almostall the vertebrcz are proccelous. The skull has many charac-teristic features, such as the unionof maxillce, palatines, and ptery-goids in the middle line on the
. Outlines of zoology. ls General Characters.— TheCrocodilians are carnivorousfresh-water reptiles of large size,now represented by a few genera, Crocodilus, Alligator, andGavialis. The skin bears epidermic scales,underneath some of which thereare dermic bones or scutes. The tail is laterally compressed,and assists in swimming. Teeth occur in distinct socketsin the premaxillce, maxillce, anddentaries. In modern Crocodilians, almostall the vertebrcz are proccelous. The skull has many charac-teristic features, such as the unionof maxillce, palatines, and ptery-goids in the middle line on theroof of the mouth, and the conse-quent shunting of the posteriornares to the very back of themouth. Some of the ribs have double articulating heads, and bearsmall uncinate processes j transverse ossifications form so-called abdominal ribs. The heart is four - chambered; a muscular diaphragmpartially separates the thoracic from the abdominal cavity. The cloaca has a longitudinal opening. The males havea grooved Fig. 348.—Lower surface ofskull of a young crocodile. ^ Premaxilla; nix., maxilla;pa-L. palatine; , os trans-versum ; pt., pterygoid;/., jugal ;(Py.,quadrato-jigal; Q., quadrate ;, posterior nares ; c, condyle. 636 REPTILIA. The Crocodilians are oviparous. The eggs have firm cal-careous shells, and are laid in holes in the ground. Skeletal system.—Numerous transverse rows of sculptured bonyplates or scutes, ossified in the dermis, form a dorsal shield. On theventral surface the scutes are absent, except in some alligators, inwhich they are partially ossified. But besides and above the scutes,there are horny epidermic scales like those in other Reptiles. The hideis often used as leather. The vertebral columnconsists of distinct cer-vical, dorsal, lumbar,sacral, and caudal verte-brae, all proccelous exceptthe first two cervicals,the two sacrals, and thefirst caudal. In mostof the pre-cretaceousCrocodilians, however,the vertebrse were amphi-coelo
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Keywords: ., bookcentury1900, bookdecade1910, bookidcu3192, booksubjectzoology
