Page:The Osteology of the Reptiles.pdf/183

Epipodials

Radius and Ulna. The two bones of the forearm or antibrachium are always complete in reptiles and movable upon each other, freely in most terrestrial reptiles, flexibly in the aquatic types, that is, without rotation of the radius; they may be more or less fixed in the chelonians (Fig. 145 a), though not crossed. The forearm in this order has a peculiar twist on the humerus by which the dorsal surface of the forearm, wrist, and hand is turned forward at right angles to the humerus without pronation or rotation of the radius (Fig. 145 a).

Fig. 133. Cotylosaur limb: Limnoscelis, left foreleg, ventral side. One fourth natural size.	Fig. 134. Ophiacodon: Anterior extremity, as mounted. One half natural size.