PLATE 12 



EXPLANATION OF FIGURES 



43 Girdle of Hexanchus. Pre- and post-omosterna. After Parker. 



44 Diagrammatic transverse section through shoulder-girdle of adult frog. 



45 Section through edges of shoulder-girdle and sternum of adult Lissotriton 

 punctatus. After Parker. 



46 Diagrammatic transverse section of arch in the Australian lizard, Trachy- 

 dosaurus rugosus. 



47 Diagrammatic transverse section of Echnidna histrix, from a mounted 

 specimen in Washington University. 



48 Anterior view of cartilaginous girdle of petrogale, 21 mm. in length. 

 The different parts of the girdle are outlined, but the whole is a continuous piece 

 of cartilage. After Broom. 



49 Transverse section of mouse embryo, 7.75 mm. long. Washington Uni- 

 versity School of Medicine series no. 102, slide 4, section 16. X 38. 



Ac, acromian PrOmSt, pre-omosternum 



Cr, coracoid PtOmSt, post-omosternum 



ECr, epicoracoid Sc, scapula 



Gl, glenoid SSc, suprascapula 



Hu, humerus St, sternum 



114 



