626 



of which forming part of the glenoid cavity he regarded as homolo- 

 gous with the posterior element in the monotremes, and the other 

 which forms most of the process as homologous with the anterior ele- 

 ment of the monotreme. The single coracoid of the reptiles and birds 

 he believed corresponded to the two elements of the monoti'eme. As 

 it was thus impossible to call either of the two elements "coracoid'' 

 he retained the name epicoracoid for the anterior, and named the 

 posterior element the metacoracoid. 



In 1887 Ltdekker from a comparison of the shoulder girdle of 

 the sloth with that of the Anomodont came to the conclusion that the 

 mammalian coracoid process is homologous with the anterior element 

 or epicoracoid of the monotreme and not with the posterior as had 

 always hitherto been believed. 



In 1899 I discussed the question in. the light of all the then 

 known facts. I showed that the coracoid process of the marsupial 

 is ossified from a single centre of ossification, that one of the two 

 elements described by Howes in the process of the higher mammals 

 is merely an epiphysis, and that the posterior of the two ventral ele- 

 ments of the monotreme is the true homologue of the coracoid of the 

 higher mammal. The two elements of the monotreme were further 

 shown to be homologous with the two found in the Anomodonts and 

 other primitive fossil reptiles and also it was believed with the two 

 ventral elements of the Anurous amphibians. For these elements the 

 proper names seem to be coracoid and precoracoid. In modern rep- 

 tiles, and birds it was believed that the precoracoid had been lost as 

 in higher mammals and that the single ventral element was the true 

 coracoid. 



In the last 13 years much additional light has been thrown on 

 the evolution of the shoulder girdle through the mammal-like reptiles, 

 and the only point on which there remains any mystery is the little 

 rudimentary element called the omosternum (Paeker). Until very 

 recently however nothing has been known of how one of the ventral 

 elements was lost in the ancestors of the modern reptiles nor which 

 element has disappeared. 



In the autumn of 1909 W. Paul Miller of Chicago University 

 made a remarkable discovery of skeletons of early Permian reptiles 

 in the Wichita Valley, Texas. These have recently been worked out 

 by Prof. WiLLiSTON and perhaps the most interesting from described 

 is Varanosaurus. Though known by nearly perfect skeletons this genus 



