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TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



the articular so that a compound lever results, with one pivot at the quadrate and the 

 other at the end of the articular; in the upper jaw the premaxilla is firmly attached to the 

 maxilla by fibrous tissue. The maxilla is attached below to the ascending process of the 

 dentary by an interarticular disc (Lubosch, 1923, p. 17). This interarticular disc is a neo- 

 morph, or new modification of the tissues normally connecting the lower end of the maxilla 

 and the outer side of the mandible. Lubosch considers {op. cit., p. 16) that the active 

 factor in this strange arrangement is the strong development of the dentary. This, how- 



Iniistiu: 

 I. niger 



Fig. 132. Iniiitius sp. 



ever, would account only for the initial phase. The close proximity of the ascending process 

 of the dentary to the maxilla is evidently due to the bending upward of the originally 

 lower border of the articular in order to lessen the adverse leverage against the powerful 

 adductors 2 and 3. Thus the gape of the mouth was reduced but a compound lever of 

 great strength was the result. It is by means of these strong pincers that the parrot-fishes 

 can tear off the seaweed and other marine growths upon which they feed. 



However, the most elaborate part of the dental apparatus of the parrot wrasses lies 

 in the throat, where the fused lower pharyngeals bear a many-toothed plate (Fig. 134) 

 against which works a corresponding but sliding plate borne by the upper pharyngeals. 

 The prolonged base of this upper plate slides back and forth on a pedestal furnished by 



