GREGORY, PRESENT STATUS OF ORIGIN OF TETRAPODA 371 



(see below), and we do not favor Broom's view that the posterior, glenoid- 

 sharing element (Fig. 12, D, E, F) in rodents, edentates and many other 



Fig. 13. — Homology of the coracoids in Monotremes 



A, Shoulder-girdle of Echidna aculeata ; B, Ornithorhynchus anatinus; left side, outer 

 view : C.D, the same, ventral view. 



The epicoracoid (ep.co) agrees with that of lizards and Sphenodon in all its relations. 

 The broad coracoid may either represent both the primitive reptilian elements (coracoid 

 and metacoracoid) or the met^coracoid may have disappeared. 



placental mammals is a neomorph, in the nature of a glenoid epiphysis. 

 This so-called epiphysis agrees with the "metacoracoid" (Williston) of 

 Permian reptiles (Fig. 14, E, F) in its relations with the true coracoid 



