ADAMS: SKULL OF THE WOLF-EEL. 347 



SUSPENSORIUM OF THE MANDIBLE. (See plate XXV.) 



The suspensorium of the mandible includes three bones — 

 quadrate, symplectic and hyomandibular. 



Hyomandibular. (Plate XXV, fig. 1; plate XXXIV, figs. 55, 56.) 



The hyomandibular is a flat bone, rectangular dorsally, with 

 a long projection extending ventrally. The outer face is con- 

 vex with a slight concavity in the center of the lower two- 

 thirds of the bone. The inner face parallels the outer and is 

 consequently concave. The dorsal edge is almost straight and 

 articulates with the pterotic. The dorsal anterior corner is 

 drawn out into a slight knob, which fits into a cavity in the 

 ventral posterior part of the sphenotic. 



The anterior edge is slightly concave in outline and articu- 

 lates with the metapterygoid. The ventral edge is extended 

 ventrally, a narrow strip of bone, rounded on the posterior 

 edge and thin on the anterior. The ventral edge is cut off 

 squarely and articulates with the symplectic. 



The posterior edge is indented by a deep notch, into which 

 the preopercular fits. The dorsal edge of this notch is drawn 

 out posteriorly into a rounded process which articulates with 

 the opercular. 



The inner face is concave and marked with striations. In the 

 dorsal part it has two large foramina and several small ones. 

 The most ventral foramen extends through the bone and comes 

 out on the exterior face in the ridge which extends down the 

 bone. 



The outer face shows more irregularities than the inner. 

 A ridge starts on the dorsal posterior edge and extends in a 

 diagonal direction down the projection. The anterior part of 

 this ridge is sharp and at right angles to the rest of the bone, 

 really making a narrow face. Another slight elevation starts 

 at the dorsal anterior corner, at the head of the hyomandibular, 

 and extending diagonally, meets the long ridge. From the 

 articulation with the opercular there is a ridge extending an- 

 teriorly and dorsally. The only foramen in the bone is placed 

 a little ventrally to the median line. It is on the ridge and has 

 a long fossa extending up to it. It goes through the bone and 

 comes out on the inner face. 



Articulatio7is. 



The hyomandibular articulates dorsally with the pterotic, 

 prootic and sphenotic. Anteriorly, with the metapterygoid. 



