OSTEOLOGY OF CAULARCHUS M.EANDRICUS (GIRARn). 2 95 



opercle, one for the preopercle (by far the largest), and one 

 divided between the symplectic and interhyal. 



The symplectic is a slender bone bridging a large open space 

 in front of the preopercle, and is the only bone between the hyo- 

 mandibular and the quadrate in this region. It is received in a 

 deep wedge-shaped notch, cut entirely to its tip, in the quadrate. 

 The mesopterygoid and metapterygoid being absent the symplec- 

 tic forms part of the anterior border of the cheek bones. In 

 Gobiesox the symplectic runs behind the quadrate as usual, cut- 

 ting from the latter only a small notch. 



FIG. I. Lateral bones of skull, a, articular; d, dentary ; h, hyomandibular ; 

 op, opercle;/, palatine; //, pterygoid ; fop, preopercle; q, quadrate ; s, symplectic; 

 sop, subopercle. 



The quadrate extends back covering the front of the pre- 

 opercle. Above it is a very large open space, nearly circular in 

 outline, bounded behind by the preopercle, and above and before 

 by the hyomandibular and symplectic. 



A small bone closely attached to the upper anterior edge of 

 the quadrate is all that remains of the pterygoid. To it the pala- 

 tine is attached by a ligament. It is very inconspicuous, and so 

 closely united to the quadrate that it appears as a part of that 

 element, but is easily separated in a macerated specimen. 



The palatine is free from the other cheek bones, and is only 

 connected to the reduced pterygoid by a ligament. Anteriorly 

 it hooks over the maxillary. 



The mesopterygoid and metapterygoid are entirely absent. 



The articular is hinged to the quadrate by a very wide hori- 

 zontal joint, making the jaw very rigid laterally. At the upper 

 posterior angle is a strong process. There is no open space be- 

 tween the articular and the upper limb of the dentary. 



