52 ELOPIFORM FISHES 



skull at the occiput is due to the dorsal development of these fossae. Epaxial trunk 

 musculature occupies the fossae and is inserted on the walls and on a stout 

 ligament which inserts on the medial surface of the autosphenotic. 



Hyopalatine bones. This series is almost as deep as long in adult specimens, but 

 in younger specimens the series is considerably longer than deep. Correlated with 

 this deepening during growth there is a slight forward shift in the quadrate/mandibu- 

 lar articulation. In the adult it lies beneath the posterior half of the orbit. 



The hyomandibular is vertical. Its head has anterior and posterior expansions. 

 The external surface of the bone is marked by a prominent ridge which ends dorsally 

 in a small dorso-lateral projection. Immediately behind this ridge there is a groove. 

 The hyomandibular nerve penetrates the medial face immediately beneath the head 

 and divides into an opercular branch and a combined mandibular and hyoidean 

 branch. The former branch leaves the hyomandibular on a level with the opercular 

 process. The latter opens into the posterior groove immediately beneath the oper- 

 cular process. The anterior border of the hyomandibular is produced into a narrow, 

 very thin wing of bone. 



The long symplectic is inclined forwards at about 45 ° and fits into a deep groove 

 upon the quadrate. The dorsal end of the symplectic overlaps the preoperculum. 

 The quadrate is the usual fan-shaped bone. Ventrally there is an enlarged, trans- 

 verse condylar surface behind which, in larger specimens, there is a shallow notch. 

 Such a notch may limit the downward movement of the mandible. The anterior 

 border of the quadrate fits into a groove on the ectopterygoid. 



The metapterygoid is separated from the dorsal margin of the quadrate by a thin 

 slip of cartilage. Upon the lateral face the metapterygoid is produced postero- 

 dorsally as a thin wing which overlaps the ventral part of the hyomandibular. 

 Between this overlap of the hyomandibular and metapterygoid there is a consider- 

 able space, the hyomandibular-metapterygoid cup, into which insert the deeper 

 divisions of the levator arcus palatini muscles. 



The endopterygoid is overlapped posteriorly by the metapterygoid. Anteriorly 

 the endopterygoid is ovoid in outline and fits between the posterior region of the 

 auto- and dermopalatine. The ectopterygoid is a boomerang-shaped element, the 

 two limbs being equally developed. The posterior and dorsal margins are grooved 

 to receive the quadrate and endopterygoid. 



The dermopalatine is a flat plate of bone partially overlapping both the endo- 

 and ectopterygoid. The medial edge of the dermopalatine lies against the border 

 of the vomerine tooth patch. An autopalatine may ossify in large individuals. An- 

 teriorly the palatine cartilage is expanded into a large knob, the dorso-medial face 

 of which contacts the cartilage underlying the suture between the dermethmoid and 

 lateral ethmoid. The antero-lateral aspect of the knob articulates with the palatine 

 head of the maxilla. Between these two elements lies a small biconcave meniscus 

 of cartilage. 



Much of the buccal face of the hyopalatine series bears teeth. Those on the pala- 

 tine are small, pointed and directed posteriorly. Upon the endopterygoid, ecto- 

 pterygoid (and, in older specimens, the metapterygoid) the teeth are slightly smaller 

 and more granular in form. In young individuals the teeth are relatively larger, 



