189] OSTEOLOGY OF LORICATI — GUTBERLET 19 



of the preopercular and between the opercular bar and the shank, the 

 other opens at the hind edge of the bone, directly beneath the opercular 

 bar. These two canals transmit branches of the nerve of the latero- 

 sensory canal which lies in the region of the opercular. Another small 

 foramen, in the dorsal edge of the groove for the preopercular, trans- 

 mits a part of the hyoid nerve between the hyomandibular and the 

 preopercular. 



Symplectic. — The symplectic is a small paddle-shaped bone with 

 a broadened end and a long slender process. It articulates at its dorsal 

 and broadened end with the shank of the hyomandibular by a long car- 

 tilaginous ligament. The bone for the most part lies in a triangular 

 groove on the lateral surface of the quadrate with its long process pene- 

 trating the bone almost to its articulating facet for the mandible. 



Metapterygoid. — The metapterygoid is a broad plate-like bone, 

 more or less quadrant shaped with two plate-like processes. The quad- 

 rant-shaped part is the ventral portion of the bone with the round edge 

 united by a cartilaginous ligament with the dorsal edge of the quadrate. 

 Two processes extend from the dorsal edge of the quadrant. One of 

 these is somewhat elongated and extends dorso-cephalad coming in con- 

 tact with the anterior process of the hyomandibular. The other extends 

 caudad from the dorso-posterior edge of the quadrant, and bears a V- 

 shaped slit for the hyoid artery on its ventral edge. The posterior edge 

 comes in contact with the anterior edge of the shank of the hyomandibu- 

 lar. Two small flanges, one on either surface of the anterior process, 

 bound a groove on the dorsal edge which extends nearly the entire 

 length of the process. The groove is for the union with the hyo- 

 mandibular. 



Quadrate. — The quadrate is a quadrant-shaped bone with the 

 ventral point thickened and formed into a head for the articulation of 

 the articular. The dorsal or rounded edge is broken near the posterior 

 edge where the bone forms a deep groove on the inner surface for the 

 articulation of the symplectic where it passes downward into the quad- 

 rate. There is a groove on the posterior edge extending almost the 

 length of the bone for the contact with the preopercular. The anterior 

 edge is somewhat roughened and possesses no groove where it articulates 

 with the mesapterygoid. On the dorsal edge the quadrate unites by a 

 cartilaginous ligament with the ventral edge of the metapterygoid and 

 cephalad with the entopterygoid and mesapterygoid, caudad it unites 

 with the preopercular and the symplectic. 



Preopercular. — The preopercular (Fig. 4) is a long, flat, curved 

 bone with three small barbs on its posterior side. A lateral line 

 sensory canal runs throughout its length, opening near the edge of the 

 ventral barb and at the dorsal tip of the bone. There are also other 



