62 



COMPARATIVE ANATOMY 



IV. EPISTERNUM. 



Episternal structures, which are wanting in Fishes, Dipnoans 

 and recent Urodeles, play an important part in fossil Amphibians 



FIG. 46. PECTORAL ARCH or VARIOUS STEGOCEPHALA (from the ventral side). 



After H. Credner. 



A, Branchiosaurus, x 3 ; B, Pelosaurus x 2 ; C, Discosaurus, x 2 ; D, Hylono- 

 mus, x 2 ; E, Archegosaurus, x about \. Ej)S, episternum ; Cl, clavicle ; 

 #, scapula ; c, coracoid ; s, calcification in the sternum or in the cartilage 

 of the coracoid. 



and primitive Reptiles (e.g., Stegocephala and Palaaohatteria), in 

 which, both as regards form and structure, they bear a great re- 

 semblance to the episternum of certain existing Reptiles. 



