88 



Morphology of the Fins 



against the homology with the scapula of any part having a 

 distant and merely ligamentous connection with the humerus- 

 bearing element. Consequently, as an element better represent- 

 ing the scapula exists, the element named scapula (by Owen, 

 Giinther, etc.) cannot be the homologue of the scapula of Ba- 

 trachians. On the other hand, its more intimate relations with 

 the skull and the mode of development indicate that it is rather 

 an element originating and developed in more intimate connec- 

 tion with the skull. It may therefore be considered, with Parker, 

 as a posttemporal. 



' ' The shoulder-girdle in the Dipnoi is connected by an azygous 

 differentiated cartilage, swollen backwards. It is more prob- 

 able that this is the homologue of the sternum of Batrachians, 

 and that in the latter that element has been still more differ- 

 entiated and specialized than that it should have originated 

 de novo from an independently developed nucleus. 



The Girdle in Fishes Other than Dipnoans. "Proceeding 

 from the basis now obtained, a comparative examination of 



FIG. 74. Shoulder-girdle of a Batfish, Ogcocephalus radiatus (Mitchill). 



other types of fishes successively removed by their affinities 

 from the Lepidosirenids may be instituted. 



" With the humerus of the Dipnoans, the element of 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 



