LEIOGNATHUS 13 



metapterygoid. Its lower .end is at a considerable distance from the 

 symplectic. 



The palatine is firmly articulated to the lower edge of the prefron- 

 tal, and bears a process which hooks over the maxillary. 



The symplectic is a short, small, triangular sliver of bone occupy- 

 ing a notch in the posterior angle of the quadrate. On its lower edge 

 not far from its posterior end is a cup-shaped cavity for the reception 

 of the interhyal. 



A well developed angular is present and forms the lower posterior 

 angle of the articular. The articular and dentary are loosely attached 

 to each other so that they are slightly independently movable in the un- 

 dissected specimen. The tooth-bearing portion of the dentary does not 

 reach nearly back to the middle of the upper edge of the bone, which in 

 most forms is completely toothed. The gape of the mouth is restricted 

 to this portion, while the posterior portion is covered by the end of the 

 premaxillary upon which it hinges. Hence the lower jaw attached at its 

 posterior end as usual, and the premaxillary attached to it in front of 

 its middle, the fish can only open its mouth by projecting the long pre- 

 maxillary processes forward from their sheath. In most fishes the max- 

 illary elements if attached at all to the lower jaw are attached so far 

 back, or so loosely, that the opening of the mouth only effects the poste- 

 rior end of them at the most. There are many examples of interme- 

 diate conditions between those described above. The mouth of Capros 

 and of many fishes of the family Chsetodontidse approaches rather closely 

 the condition of Leiognathus. 



The maxillary is a complex-shaped bone, shaped roughly like the 

 figure 3. It meets its fellow above the premaxillary process, and nearly 

 meets it below, thus forming a sheath in which the process moves. 



A small, round nodule of bone represents the interhyal. It is 

 rather firmly bound down to the epihyal by tissue. It fits into the cup- 

 shaped cavity in the lower edge of the symplectic remote from the hy- 

 omandibular, instead of between the hyomandibular and the symplectic 

 as is the usual arrangement. But the chief articulation of the hyoid 

 arch to the lateral head bones is through the interopercle. This element 

 is thickened along its upper edge, and about midway in its length is a 

 prominent facet, partly sunk below the surrounding surface of the sur- 

 rounding bone and partly raised above it. To this the posterior end of 

 the epihyal is firmly articulated by a specialized articular facet. The 

 hypohyals are paired on each side. A glossohyal and urohyal are pres- 

 ent, the latter with wings standing out horizontally from its lower edge. 



There are three tooth-bearing superior pharyngeals on each side. 



