. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. MOTION. 449 land and water. The outline of the Sauria presents a lengthened form, having the atlanto- sacral axis much greater than the transverse; they partake more of the figure of the Ophidian than of the Chelonian reptiles, but differ from the former in having legs for the support of the trunk and for locomotion, and also in having a more complex skeleton, including besides the vertebral and costal bones, scapulae, clavicles,* sternoid, pelvic, and sacral elements, as in mammiferous quadrupeds. The acetabula of the s
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. MOTION. 449 land and water. The outline of the Sauria presents a lengthened form, having the atlanto- sacral axis much greater than the transverse; they partake more of the figure of the Ophidian than of the Chelonian reptiles, but differ from the former in having legs for the support of the trunk and for locomotion, and also in having a more complex skeleton, including besides the vertebral and costal bones, scapulae, clavicles,* sternoid, pelvic, and sacral elements, as in mammiferous quadrupeds. The acetabula of the scapulae and ossa ilii are inclined horizontally outwards; the humerus and femur, which are short, take the same direction; the ginglymoid articulations of the elbow and knee joints are inclined backwards eccentrically to those of the shoulder and thigh. The effect of this is that the extension and flexion of the fore-arm and leg, being made in the plane of the trans- verse horizontal section of the body, are at the same time movements of abduction and ad- duction ; an arrangement which renders the ex- tremities ill adapted for rapid progression on land. Those Sauria which have the four legs nearly of an equal length may be considered '.he best adapted for locomotion ; the vertebral column being in this case parallel to the plane of motion. When the legs are nearly of equal length, the bone? of the an tenor and posterior ex- tremities bear the following proportions : in the arm of the Crocodilus acutus the liumerus is found to be , the ulna 3 083; and in the leg, the femur , the tibia inches, so that + — — = — inch for the difference of the length of these bones. The metatarsus and toes are longer and broader than the carpus and phalanges of the fingers, and present a large surface to strike the water in The posterior extre- mities of the Biporcatus are palmated,} those of the Caymati semipalmated. The legs of the Sauria
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