124 



TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



Acentrophorus varians 



leboti^ ^ 



posforb 



^\,^supcL 



po- ros 



ros 





Perleidus woodward.! 



Fig. 21. Comparison of the most progressive known pal;eoniscoid Perleidus (A) of the Triassic family Catopteridse (after 

 Stensio) with the most primitive semionotid, Jcenlrophorus (B) of the Permian and later periods (after E. L. Gill). 



In the advanced palaeoniscoid the suspensorium is intermediate in position and the postorbital series is beginning. In the 

 primitive semionotid the suspensorium is inclined forward and the postorbital series is well developed. 



