770 DR R. BROOM ON THE DEVELOPMENT OF MARSUPIAL SHOULDER GIRDLE 



Fig. 4. Outer view of shoulder girdle of 17 mm. Trichosurus embryo, x 21. The limit of commencim 

 ossification is shown by interrupted lines. 



Fig. 5. Ventro-lateral view of shoulder girdle of 14 "8 mm. Trichosurus embryo, x 27. 



Fig. 6. Anterior view of shoulder girdle of 16 mm. Pseudochirus embryo, x 18. 



Fig. 7. Anterior view of shoulder girdle of 1 7 mm. Trichosurus embryo, x 20. 



Fig. 8. Trans, vert. sect, of shoulder girdle of 1 7 mm. Trichosurus embryo, x 20. The dark shadinj 

 indicates the region where the cartilage is about to ossify ; the medium shading, normal hyaline cartilage 

 the light shading, the portion of coracoid cartilage undergoing degeneration. 



Fig. 9. Anterior view of shoulder girdle of 21 mm. Petrogale embryo, x 17. 



Plate II. 



Fig. 10. Ventral view of shoulder girdle of 14 - 8 mm. Trichosurus embryo, x 34. 



Fig. 11. Ventral view of shoulder girdle of 17 mm. Trichosurus embryo, x 28. 



Fig. 12. Ventral view of shoulder girdle of 16 mm. Pseudochirus embryo, x 30. 



Fig. 13. Ventral view of shoulder girdle of 21 mm. Petrogale embryo, x 28. 



Figs. 14-22. A series of specimens illustrating the phylogeny of the coracoidal elements. Variousl 

 magnified and reduced. 



Fig. 14. Coracoid and Precoracoid of the Common Toad (from nature). 



Fig. 15. Coracoid and Precoracoid of Procolophon (modified after Seeley). 



Fig. 16. Coracoid and Precoracoid of Dicynodon (modified after Seeley and Lydekker). 



Fig. 17. Coracoid and Precoracoid of Gomphognathus (restored from fragments in Brit. Mus.). 



Fig. 18. Coracoid and Precoracoid of Ornithorhynchus (from nature). 



Fig. 19. Coracoid and Precoracoid of Echidna (from nature). 



Fig. 20. Coracoid of Embryo Trichosurus (reconstructed from sections). 



Fig. 21. Coracoid of nearly adult Pseudochirus (from nature). 



Fig. 22. Coracoid and Epiphysis of Cape Hare (from nature). 



