32 



tion superior to that of Fishes. In the hulbus arteriosus a longitudinal 

 projection appears as a commencing division of the single artery, 

 which is given off from the ventricle. 



The differences in the structure of the preceding parts, and in the 

 origin and distribution of the different vessels exhibited by the other 

 genera of Perennlbranchiata, were successively noticed ; and the affini- 

 ties indicated by these modifications to the Caducibranchiate Reptiles 

 on the one hand, and to the Cartilaginous Fishes on the other, were 

 also pointed out. 



The Paper wa.s illustrated by drawings of the structures described 

 in it. 



