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TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



obliquely backward and downward as in hyostylic sharks. The derm bones are reduced, 

 almost vestigial. In spite of this specialization, however, the palaeoniscoid heritage is 

 still very evident, as noted by Traquair. The so-called opercular bone corresponds in 

 position with the subopercular of the palaeoniscoids and chondrosteids, and possibly the 

 true opercular, already small in palaeoniscids, has disappeared. 



nasalo- 

 ant orbital 



hot 



parietal / 

 ■parietal Z 



lai line 

 canal 



Saurlchthys ornatus 



Fig. 16. Saurichtkys ornatus. After Stensio. 



A. Side view. Stensio's nomenclature somewhat modified to accord with system adopted herein. 



B. Top view. According to Stensio, the bone marked plo represents a combination of the supratemporal (= pterotic), inter- 



temporal and eztrascapular (scale bone). 



