138 ALUS. [Vol. XVIII. 



one oblique, or even longitudinal. The oblique portion lies be- 

 tween, and connects, the other two, which are one dorsal and the 

 other ventral to it, the dorsal one lying proximal, or posterior, to 

 the ventral one. The transverse surfaces on both bones are cap- 

 ped with cartilage. The oblique portion is not so capped. 



The Hypohyal (HH) contains, as above stated, two separate 

 ossifications. They are united by a narrow line of cartilage which 

 starts from near the dorsal edge of the proximal, posterior end of 

 the piece and runs distally to about the middle of its distal end. 

 The dorsal ossification is thus the smaller of the two. At the 

 dorsal corner of its distal end it has, on its mesial surface, 

 a strong process, usually conical in shape, with a pointed end 

 directed mesially and backward. It is strongly but loosely bound 

 by fibrous or ligamentous tissue to its fellow of the opposite side 

 of the head, the two processes, so united, lying antero-dorsal to 

 the cartilaginous anterior end of the first basibranchial, and ventral 

 to the hind end of the basihyal. On their ventral surfaces both 

 processes are slightly hollowed, and there articulate with the end 

 of the first basibranchial. 



At the inferior corner of the distal end of the ventral ossification, 

 there is a rounded eminence, and slightly proximal to it, on the 

 ventral edge of the ossification, another eminence. The latter 

 eminence gives insertion to a ligament that has its origin from the 

 anterior end of the sternum, and that corresponds to the tendinous 

 end of the sterno-hyoideus muscle ^of Amia. The anterior emi- 

 nence is capped with cartilage and articulates, in the middle line 

 of the head, ventral to the anterior end of the basal line, with the 

 corresponding process of the hypohyal of the opposite side. On 

 the lateral surface of this same ossification, adjoining the process 

 that gives insertion to the ligament from the sternum, there is a 

 slight depression which indicates the surface of insertion of the 

 anterior tendinous end of the hyohyoideus muscle of the opposite 

 side of the head. On the mesial surface of the entire element, in 

 the cartilaginous line that separates its two ossifications, and some- 

 what distal to the middle point of the line, there is a round fora- 

 men. It is the internal aperture of a canal that leads backward and 

 laterally through the element, between its two ossifications, and that 

 gives passage to the arteria hyoidea. Having reached the external 



