6 



MUSEO NACIONAL DE BUENOS AIRES. 



cali tlie coracoidal elemeiit in the shoulder-girclle of the SlotL. 

 the epicoracoid. This is in harmony with. tlie conclusión of Pro- 

 fessor Howes, wlio in tlie j)aper cited (p. 404) observes tliat 

 «tlie coracoid process of the Marsiipialia and Placentalia is tlie 

 homologue of the Monotreme's epicoracoid». ^Tien, however, he 

 proceeds to add that the exclusión of this epicoracoid from the 

 glenoid cavity is one of its most characteristic features, I niust 



take leave to differ from him. It is 

 true that in the Monotrenies (as 

 shown in fig. 3 of the drawing) the 

 so-called epicoracoid (c) — which 

 all are agreed as representing the 

 epicoracoid of the Dicynodont — is 

 excluded from the glenoid cavity; 

 hut this appears to me to be due to 

 its having been pushed forwards an 

 bent downwards into the ventral 

 plañe of the body. Both the Dicy- 

 nodont (in spite of what is urged 

 bj^ Professor Howes) and the Bra- 

 dypodine so-called epicoracoid en- 

 ter to a small extent into the for- 

 mation of the glenoid cavity^. » 



«We have it, then, that the hu- 

 man coracoid is homologous with 

 the so-called epicoracoid of Bra- 

 dyptis, Dicynodon, and EcTiidna; 

 while the element termed coracoid 

 in the two latter, as articulating 

 with the sternum, represents the 

 element so named in the Sauropsida. 

 Here, however, as has been pointed 

 out to me by my friend Mr. Thomas, a new difficulty arises. The 

 coracoid element was first named from the coracoid process of 

 man, and therefore, undoubtedly, the bone which we have called 

 epicoracoid is the true coracoid; while the element to which the 

 latter term is applied in the Monotremes and Saurojjsida is pro- 



nirvc 



fig. 3. Echidna. Omoplato dere- 

 cho: »c, escapular; c, coracoideo ; 

 me, metacoracoideo ; a, acromion; 

 gl, cavidad glenoides. 



1 I may mention that I am indepted to Professor Howes for pointing out that 

 I have incorrectly identif ied the acromion in the scapula of Z)¿V</no(7o)i, tho true 

 acromion being the one lettered a in the accompan3-ing figure. 



