On the Tarsus and Carjms of Birds. 155 



Fig. 4. Tardus fascescens. Embi\yo not given. 



A later stage in which the proximal tarsals have already uuited with 

 the tibia, and the distal tarsal has not yet united with the metatarsals. 



Fig. 5. Tardus fascescens. 



Another view of the same. 



Fig. 6. Ti/rannus Carolinensis. E. 23. 



The tibiale and fibiilare united with tibia, the centrale still free. 



Fig. 7. Dendrmca cesliva. E. 24. 



The two proximal tarsals uuited. The centrale very large and capping 

 the three metatarsals. 



Fig. 8. Dendrceca msiiva. 



Another view of the same, showing the tarsal bones more distinctly. 



Fig. 9. Dendrosca cestiva. 



Another view of same, showing centrale capping the metatarsals. 



Fig. 10. Quiscalus versicolor. E. 25. 



The tibiale and jibulare united, but not yet auchylosed to the tibia. 

 The centrale still free. 



Fig. 11. Qaiscalus versicolor. 



An enlarged view of the tarsus. 



Fig. 12. Sialia sialis. E. 31. 



The proximal tarsals united with the tibia. The distal tarsal united 

 with the fourth metatarsal. 



Fig. 13. Sialia sialis. 



Another view of the same. 



Fig. 14. Cotyle riixiria. E. 27. 



A considerably advanced stage in which the three tarsal bones are 

 distinctly separate. 



Fig. 15. Hirundo lunifrons. E. 30. 



The tibiale and Jibulare about uniting. The centrale already blended 

 with third metatarsal. 



Fig. 16. Tringoides macularius. E. 26. 



The tibiale and fibulare united forming an hour-glass shaped bone. 

 The centrale flattened and capping the metatarsals but not yet united with 

 them. 



Fig. 17. Tardus migratorius. 



Posterior portion of early embryo, sliowing the leg as a simple fin, 

 and caudal vertebrae. 



