of the Shoulder-girdle of Fishes. 175 



We may therefore regard it, with Parker, as a post- 

 temporcd. 



VI. The shoulder-girdle in the Dipnoi is connected by an 

 azygous differentiated cartilage, swollen backwards. 



It is more probable that tliis is the homologue of i\\Q, sternum 

 of Batrachians, and that in the latter that element has been 

 still more differentiated and specialized, than that it should have 

 originated de novo from an independently developed nucleus. 



The homologies of the elements of the shoulder-girdle of the 

 Dipnoi appear then to be as follows : — 



Tlie Girdle in other Fishes. 



Proceeding from the basis now obtained, a comparative 

 examination of other types of fishes successively removed by 

 their affinities from the Lepidosirenids may be instituted. 



I. With the humerus of the Dipnoans the element in the 

 Polypterids (single at the base but immediately divaricating, 

 and with its limbs bordering an intervening cartilage) which 

 supports the pectoral and its basilar ossicles must be homolo- 

 gous. 



But it is evident that the external elements of the so-called 

 carpus of teleosteoid Ganoids are homologous with that element 

 in Polypterids. 



* Gelenkstelle der Brustflosse am primiiren Scliulterknorpel (Gegen- 

 baur). 



t Clavicula (Gegenbaur). 



X Verbindungsstelle des beiderseitigen Schulterknorpels (Gegenbaur). 



Prof. Gegenbaur regards the median cai'tilage as a dismembennent of a 

 common cartilage, tlio upper division of which receives the pectoral limb, 

 while the lower unites with the corresponding dismemberment of the 

 opposite side and forms the median cartilage. 



§ The suture separating the " coracoid " into two poi-tions has been 

 observed by Dr. Giinther, but he could " not attach much importance to 

 this division." 



