Page:The Osteology of the Reptiles.pdf/177

(Fig. 141) is saddle-shaped, permitting motion in two planes only—antero-posterior and dorso-ventral.

Fig. 130. Seymouria (Cotylosauria). Humerus, femur, tibia. A, right humerus, a from side, b from front; B, left tibia, ventral side; C, radius; D, right femur, from behind; E; left femur, from Cacops bone-bed, natural size; F, undetermined.

At the upper or proximal end of the bone, near its articular part, are two more or less prominent processes for the attachment of muscles. That on the preaxial ventral side (Fig. 131), usually situated above the middle third, but often descending nearly to the middle or even below the middle in stout-limbed reptiles, is the