i_,_0 ALUS. [Vol. XVIII. 



two ossifications of the ceratohyal, there lying dorsal to the splint 

 processes that connect those ossifications, and, having reached the 

 distal end of the element, joins the end of the groove that lies 

 between the two ossifications of the hypohyal. It lodges the 

 arteria hyoidea, after that arter}- issues from the canal through the 

 hypohyal. 



The adjoining edges of the two ossifications of the ceratohyal 

 are slightly rounded, this being most marked toward the ventral 

 edge of the element. In the middle line of the cartilaginous inter- 

 space that lies between the two ossifications there is some slight 

 indication of the beginning of the formation, or the end of the ex- 

 istence, of a separating line. 



The Epihyal (EH), or interhyal, is a small bone the distal 

 end of which is large and flat, the proximal end small and rounded. 

 In its natural position it lies directed dorsally and slightly forward, 

 approximately at right angles to the long axis of the ceratohyal, 

 and in the direction of a ventral continuation of the axis of the 

 ventral end of the hyomandibular. By its dorsal end it articu- 

 lates with a facet in the interspace of cartilage that lies between 

 the hyomandibular and symplectic. On the posterior half or two 

 thirds of its ventral end there is a rounded cartilaginous eminence 

 which articulates with the facet on the dorsal edge of the proximal 

 end of the ceratohyal. The anterior half or third of its ventral 

 end is not capped with cartilage and forms a sort of process which 

 abuts against the edge of the ceratohyal and so limits the motion 

 of the joint. The process gives attachment to a part of the artic- 

 ular ligament of the joint. 



The Hyomandibular (HMD) is, roughly, a strong rod of 

 bone lying inclined downward and slightly backward, and having, 

 close to its dorsal end, two strong processes, one directed forward 

 and slightly upward, and the other almost directly backward. The 

 dorsal end of the rod itself, and the ends of both its processes, are 

 capped with cartilage and form articular heads. The articular 

 surface on the dorsal end of the rod itself is oval in form, the long 

 axis of the oval directed downward, forward and mesially. It 

 articulates with the lateral surface of the skull, near its dorsal 

 edge, in the long facet on the ventro-lateral surface of the 

 squamosal. The articular surface on the anterior process is 



