100 



A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA 



The hind limb (from Williston's description): "The femur and tibia resemble 

 those of Labidosaurus. The fibula is strongly curved with a considerable expan- 

 sion at its lower extremity, and with a small, rounded upper end. In the foot a 

 large flat fibulare articulates with the fibula of the right side in position, closely 

 articulating on the inner side with another large bone, evidently the united tibiale 

 and intermedium. Four tarsal distalia are visible. The shapes of the bones 

 distinguished agree in general so well with those of Labidosaurus, as figured by me, 

 that I have no hesitation in giving the others from the same genus, shaded in 



Fig. 45. — Restoration of Captorhinus. After Williston. 



the figure (fig. 45). The tibiale, however, must have been shorter than in Labido- 

 saurus. As regards the toes, all five metatarsals are visible on one or the other side, 

 and many of the phalanges, save those of the fifth toe. In the figure given in the 

 restoration (fig. 45) the unshaded phalanges are given precisely in the positions 

 they occupy with regard to the tarsus, so that the length of the toes is quite certain. 

 Those phalanges which can not be extricated from the matrix are shaded. In all 

 probability the phalangeal formula is like that of the front feet; certainly there can 

 not be a greater number." 



The ribs: A small rib is present on the axis, and there was probably one on the 

 atlas, but this is not known. The third cervical carries a large rib, with the proximal 

 end broad and thin, but not divided into capitulum and tuberculum; immediately 



