202 ALUS. [Vol. XVIII. 



hyomandibular is pierced by the truncus hyomandibularis facialis, 

 which runs upward, from its foramen, close against the lateral 

 wall of the skull. That pa:rt of the united muscles that lies an- 

 terior to the truncus facialis forms much the larger part of it. 

 It arises (Fig. ii) from that part of the lateral surfaces of the 

 petrosal and the lateral wing -of the parasphenoid, that lies in 

 front of a nearly vertical line drawn from the dorsal surface 

 of the muscle downward across the hind edge of the facial 

 foramen and then along the anterior edge of the slight groove 

 that marks the position of the infrapharyngobranchial of the first 

 arch. The surface of origin does not extend quite to the dorsal 

 edge of the petrosal. Antero-ventrally it extends forward along 

 the dorsal edge of the lateral surface of the body of the para- 

 sphenoid some little distance in front of the anterior edge of the 

 wing of the bone. That part of the united muscles that lies 

 posterior to the truncus facialis arises from a small part of the 

 lateral surface of the petrosal, extending backward and upward 

 to the posterior edge of the bone near its dorsal end, and from a 

 small adjoining portion of the anterior edge of the lateral sur- 

 face of the squamosal, the hind edge of the muscle here being 

 contiguous with the anterior end of the adductor operculi. The 

 surface of origin of the entire muscle thus has an anterior, ventral 

 portion, a posterior, dorsal portion, and a vertical portion con- 

 necting the two. The dorsal surface of the muscle is covered by 

 the partly tendinous membrane that, in part, seems to present 

 the first and second divisions of the levator maxillse superioris, 

 the membrane, near the origin of the adductor, being attached to 

 its outer surface and seeming to serve in part as origin for it. 



The fibers of the anterior and ventral part of the muscle run 

 outward, or outward and forward, and are inserted on the inner 

 surface of the dorsal edge of the metapterygoid along its entire 

 length, the surface of insertion occupying the groove, already 

 described, on the edge of the bone. These fibers are, therefore, 

 that part of the muscle that corresponds to the separate adductor 

 arcus palatini of certain other fishes. Anteriorly, this part of 

 the muscle lies dorsal to the hind end of the entopterygoid, be- 

 tween it and the eyeball ; posteriorly and mesially it lies im- 

 mediately dorsal to the lining membrane of the roof of the mouth. 



