1893.] Clavicular Arch in Tchthyosauria and Sauropterygia. 153 

 pc. 



FiG. 2. Left shoulder girdle of Pareiasaurus Baini as the bones were found before 

 the matrix had been removed to separate the clavicular arch from the 

 scapular arch, ic., interclavicle ; Cl. t clavicle ; pc., precoracoid j cor, 

 coracoid; Sc., scapula; ec., epiclavicle. 



CCL. 



Sc. 



FfG. 3. Shoulder girdle of a young Ornithorhyncus, after GK B. Howes, reduced 

 and reversed. The dotted parts (Ca.) are cartilage; Cl., clavicle; pc, 

 precoracoid ; c, coracoid ; Sc., scapula ; gl., humeral articulation. 



these groups of animals, living or extinct, then it would, from the 

 analogy of shoulder girdles which from age or plan are imperfectly 

 ossified, be a legitimate inference, I submit, that the foramen which 

 was defined on the one side by bone was completed on the other 

 side by cartilage. The notch is in such a position that it is com- 

 parable to a coracoid foramen. No other determination for it has 

 been suggested. If this identification were admitted, it seems to 

 me highly probable, from comparison of the scapular arches in extinct 

 Sauromorpha, that the cartilage which extended inward from the 

 scapula was continuous with the cartilage which extended forward 

 from the coracoid, and that the intermediate part defined the anterior 

 margin of the foramen. If I understand Mr. Hulke, he would admit 

 the existence of such a cartilage as an inference supported by analogy ; 



