THE SKELETON OF REPTILES 



35 



in those reptiles allied 

 to the ancestors of the 

 mammals has the 

 scapula ever had a 

 spine or projection on 

 its dorsal side. 



Of the two coracoid 

 bones in the original 

 pectoral girdle the 

 posterior one began 

 to disappear early and 

 is entirely lost in all 

 reptiles that lived later 

 than Triassic times, 

 though it still persists 

 in the lowest mam- 

 mals, as we have seen. 

 In most later reptiles 

 the remaining coracoid 

 has become less firmly 

 attached to the scapula 

 than it was in the older 

 reptiles. It usually 

 has a small foramen 

 piercing it near the 

 middle of the upper 

 border or end, the 

 supracoracoid fora- 

 men. The clavicle, 

 while more constant 

 among reptiles than 

 among mammals, has 

 been lost in some, the 

 Crocodilia, for in- 

 stance, as also the 

 dinosaurs and ptero- 

 dactyls. The inter- 

 clavicle is more 



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