144 ALUS. [Vol. XVIII. 



near the ventro-posterior edge of that bone, the groove extend- 

 ing downward and forward to the base of the articular head of the 

 element. The inferior end of the symplectic is pointed with carti- 

 lage. The internal surface of the bone lies flush with the 

 internal surface of the quadrate. The external surface of its 

 dorsal end lies flush with the external surface of the metapterygoid. 

 The line of cartilage that edges the latter bone fits into a groove on 

 the anterior edge of the symplectic, the mesial edge of this groove 

 being produced as a flat process, which overlaps internally the 

 strip of cartilage and also the hind edge of the metapterygoid be- 

 yond it. 



Between the hind edge of the dorsal end of the symplectic and 

 the anterior edge of the dorsal end of the postero-dorsal process 

 of the quadrate, there is a space, which transmits the ramus 

 mandibularis externus facialis from the outer surface of the 

 hyomandibulo-symplectic to the inner surface of the palato-quad- 

 rate. Between the hind edge of the remaining, ventral portion of 

 the symplectic and the hind edge of the groove of the quadrate in 

 which it lies, there is a narrow space, which forms a channel in 

 which the mandibularis externus facialis lies in the beginning of 

 its course along the inner surface of the palato-quadrate. The 

 mandibularis internus facialis reaches the inner surface of the 

 palato-quadrate through a canal {miffr, Fig. 36) that lies between 

 the anterior edge of the symplectic and the adjoining portions of 

 the metapterygoid and quadrate. The symplectic thus lies be- 

 tween the two nerves, as it does in Amia. 



The Interspace of Cartilage between the hyomandibular 

 and symplectic is small, and is deeply hollowed on its postero-ven- 

 tral edge by the articular facet for the epihyal. At its anterior 

 edge it is continuous with the line of cartilage that first edges the 

 hind edge of the metapterygoid and then lies between that bone 

 and the quadrate. The hyomandibulo-symplectic cartilage is 

 thus, in the adult Scoinher, fused with the palato-quadrate, as Pol- 

 lard says it is in the young of certain other teleosts (No. 60). 



The Preoperculum (POP) is a large, somewhat crescent- 

 shaped bone, with the hollow of the crescent directed forward and 

 upward. The dorsal portion of its anterior edge lies in the 

 groove on the hind edge of the hyomandibular, the bluntly pointed 



