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TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



that the highly peculiar opercular of the former is a neomorph, developed within narrow 

 taxonomic limits. 



At the other extreme of the notothenioid series stands the deep-sea family of the 

 Chsenichthyidae which have depressed, somewhat duck-like, non-protruslle snouts (Fig. 

 239C). The palatopterygoid arch Is reduced to a thread; the opercular bears several 



C Bovlchthys varie^atus 



hyom 



A Notothenia corliceps " 'B Cottoperca 3obio 



Fig. 240. Opercular region of Notothinxa (A), Cottoperca (B), Bovichthyj (C). 



posterior spines, of which the most dorsal one appears to correspond with the dorsal process 

 of the opercular of Bovlchthys. 



As seen from above, the skulls (Fig. 241) of notothenioids vary from fairly broad to 

 long and narrow, as shown in the following figures : 



In the otoliths of the more primitive Nototheniiformes, according to Frost (1928fl, p. 

 454), the sagiuta is of the labrid type resembling that of Scarus abildgaardii in general 

 features. This may possibly mean that the notothenioid group came off from the percoid 

 stock near the labrid branch, or to put it another way, that the labrids, notothenioids and 

 trachinoids may have diverged from such a relatively primitive percoid type as the Pinguipes 

 or its ally Parapercis. 



