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TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



and does break into live bivalve shells and secure the contents. Here then the high value 

 of the mechanism in terms of natural selection must be admitted. 



Hoplegnathus. — This is the type and sole genus of a peculiar family of percoids that is 

 probably allied with the Lutianidae (Tate Regan, 1913a, p. 130; 1929, p. 321). The out- 

 standing feature of this skull (Fig. 124) is the coalescence of the teeth on the premaxillae 

 and dentaries into a powerful beak. The maxillae, unlike those of other beaked teleosts, 

 are much reduced but evidently still serve for the insertion of the tendon of the superficial 



.epiot 

 scale bon« 

 ...ptm 



Hoplegnathus 



Fig. 124. Hoplegnathus. 



branch {A 1) of the adductor mandibulae muscle, which would run obliquely downward and 

 backward. Thus its course would cross that of the deep adductors inserted on the articular. 

 Contraction of the entire muscle mass would thus pull powerfully upward on the mandible 

 and downward on the premaxillae. 



The upper beak rests on the enlarged ethmo-vomer, which is braced principally by the 

 parethmoids, parasphenoid, palatines and frontals. The dentary, as in other beaked types, 

 tends to form a secondary joint with the articular. The skull is deep, the supraoccipital 

 towering on top and the opercular region extending downward. Although the articular- 

 quadrate facet is located far forward, beneath the anterior border of the orbit, the mouth 



