234 



THE BIOLOGY OF THE FROG chap. 



prominence, the coronoid process, which gives attachment to 

 the muscles for closing the jaw. 



The dentalc lies on the outer side of the distal end of the 

 angulare, overlapping Meckel's cartilage, which there runs 

 between these two bones. The apical portion of the man- 

 dibular arch consists of two short movable elements, the 

 7iic7ito-meckelian bones, which result from the ossification of 

 the distal portions of Meckel's cartilage. They underlie the 

 premaxillaries, and when they are raised, cause a correspond- 

 ing elevation of the latter bones. 



The Hyoid. — The branchial skeleton of the frog is com- 

 posed of the hyoid cartilage and its processes. The body 

 of the hyoid is a large flat plate of hyaline cartilage, more 

 or less quadrate in general outline, lying in the floor of the 

 buccal cavity. Its anterior margin, where the base of the 

 tongue is inserted, is strongly concave. At the anterior end 

 of the body arise the anterior cornua, which are long, slen- 

 der rods of cartilage, which pass backward and upward on 

 either side of the throat and join to the prootic bones of the 

 skull. 



On the inner side of the base of each cornu is a short 

 anterior process. The alary processes, flattened, distally 

 expanded plates of cartilage, arise just behind the anterior 

 cornua. The postero-lateral angles of the body are produced 

 to form the postet'o- lateral processes. The thyroid processes 

 diverge from the middle part of the posterior margin of the 

 body and lie on either side of the larynx, which they help to 

 support. They are the only parts of the hyoid apparatus to 

 become ossified. 



The Cartilaginous Cranium. — The skull of the frog is 

 composed of cartilage to a much greater extent than in the 

 higher vertebrates. Only here and there does its origi- 

 nal cartilaginous basis become converted into bone. The 



