186 



THE VERTEBRATE SKELETON. 



(b) displacement of structures, e.g. in Bufo viridis, the 

 centrale has been pushed up till it comes to articulate with 

 the radius, 



(c) the development of supernumerary elements, especially 

 of extra centralia. In Megalobatrachus two or even three 

 centralia sometimes occur. 



FIG. 31. A, EIGHT ANTIBRACHIUM AND MANUS OF A LARVAL SALAMAN- 

 DER (Salamandra maculosa) (after GEGENBAUR). 

 B, EIGHT TARSUS AND ADJOINING BONES OF Molge sp. (after 

 GEGENBAUR). 



1. radius. 11. tibia. 



2. ulna. 12. fibula. 



3. radiale. 13. tibiale. 



4. intermedium. 



5. ulnare. 



6. centrale. 



7. carpale 2. 



8. 3. 



14. intermedium. 



15. fibulare. 



16. centrale. 



17. tarsale 1. 



18. tarsalia 4 and 5 fused. 



9. 

 10. 



I. II. III. IV. V. digits. 



In the great majority of Amphibia while one digit, 

 probably the first, is absent, the other four digits are well 

 developed. In the forms however with degenerate limbs like 

 Amphiuma, Siren and Proteus the number of digits is still 



