154 • ALUS. [Vol. XVIII. 



The groove on the inner surface of the quadrate lodges the sym- 

 plectic, but, as already stated, it is not entirely filled by that bone, 

 a narrow space being left between the symplectic and the anterior 

 edge of the dorso-posterior process of the quadrate. This space 

 transmits the ramus mandibularis externus facialis from the outer 

 to the inner surface of the palato-quadrate arch ; and the arteria 

 hyoidea in the contrary direction. A small canal between the an- 

 terior edge of the symplectic and the adjoining part of the quad- 

 rate, in the angle between the body of the latter bone and the base 

 of its dorso-posterior process, transmits the ramus mandibularis 

 intemus facialis from the outer to the inner surface of the arch. 



The hind edge of the quadrate, posterior to the groove that 

 lodges the symplectic, projects posteriorly as a flat process that 

 lies in the level of the mesial surface of the element. The dorso- 

 posterior process of the quadrate is a dorsal continuation of this 

 flat process. Lateral, or superficial, to the flat process, the hind 

 edge of the bone is slightly grooved. This groove lodges the 

 anterior edge of the ventral end of the preoperculum, the two 

 bones being firmly bound together. 



Dorsally the quadrate is separated from the ventral edge of the 

 metapterygoid by the line of cartilage already described, and 

 antero-dorsally it bounds the interspace of cartilage in front of the 

 latter bone. Its ventro-anterior edge is bevelled and fits against 

 the outer surface of the hind edge of a part of the ectopterygoid. 



The Ectopterygoid (ECP) is a somewhat Y-shaped bone, the 

 shank of the Y forming the anterior end of the bone and 

 lying in a nearly horizontal position. This shank is, in 

 transverse section, convex on its antero-inferior edge and con- 

 cave on its superior edge, the concavity becoming more pro- 

 nounced toward the foot of the shank, that is toward the 

 anterior end of the bone, the bone there being thin, and looking 

 like a delicate gouge. The arms of the Y are flat and pointed, 

 and lie at more than a right angle to each other. The lower arm 

 is much the stouter of the two, is directed downward and back- 

 ward, and extends nearly the full length of the antero-ventral 

 edge of the quadrate. Its posterior edge is bevelled to receive the 

 anterior edge of the latter bone, which it overlaps internally. The 

 dorsal arm of the Y is directed backward and slightly upward, 



