THE PECTORAL AND PELVIC GIRDLES 



131 



Fig. 103. Pectoral girdle of Ichthyosaur, Baptanoden {Ophthalmosaurus). 

 After Gilmore. 



Fig. 104. Pectoral girdle of Champsosaurus (Choristodera), 

 After Brown. 



Interclavicle. The interclavicle in the earhest-known reptiles (Fig. 

 96 B, c, d) is an elongate bone with a dilated but not T-shaped an- 

 terior extremity. The stem underlies the approxi- 

 mated mesial borders of the coracoids, usually ex- 

 tending beyond them. In a specimen referred to 

 Pantylus (Fig. 105), a primitive cotylosaur, the 

 interclavicle is forked in front and somewhat fan- 

 shaped behind, shaped very much like that of the 

 monotremes. In the later cotylosaurs the front end 

 is more dilated, as usual with all later reptiles. In 

 the known forms of the Therapsida (Fig. 107 c) the 

 shape is usually like that of the Theromorpha and 

 Cotylosauria. It is very short and fan-shaped in F'°- ^°^- P""^^^ 



(Cotylosauna): inter- 



Lystrosaurus of the Anomodontia (Fig. 94 d), where clavicle («v/) and cor- 

 Broom attributes its reduction to water habits. ^"^""^ ^'°^''' 



size. 



Natural 



