THE SESAMOID ARTICULAR 



21 



process from it joins the inner surface of the ectosteal plate of the articu- 

 lar, but does not articulate with the endosteal process. The tendon is 

 large. 



Amiurus catus. 



A very large sesamoid articular is present. It is fitted saddle-like 

 around the upper part of Meckel's cartilage. Its inner edge is articulated 

 by a dentate suture with the inner edge of the endosteal process of the 

 articular which covers the posterior part of Meckel's cartilage. Its outer 

 surface lies flat against the inner surface of the ectosteal plate. It thus 

 forms the roof of a cavity for Meckel's cartilage, the inner side wall of 

 which is formed by the endosteal part of the articular. 



Platystomatichthys sturio. 



The sesamoid articular overlies the upper edge of Meckel's cartilage, 

 and is articulated with the endosteal process but does not extend to the 

 ectosteal plate of the articular. The tendon is attached to the extreme 

 posterior upper corner of it. 



Brachyplatystoma vaillanti. 



Meckel's cartilage turns upward to the point of the coronoid process. 

 A large sesamoid articular overlies the cartilage at a point where it 

 turns up from the typical horizontal portion. It is articulated with the 

 endosteal process of the articular, and arching over the cartilage attaches 

 itself to the inner face of the ectosteal plate. Posteriorly, a little above 

 its middle, is a blunt tubercle of bone to which the tendon is attached. 



Fig. 9. BRACHYPLATYSTOMA VAILLANTI 



d, dentary; ecpl, ectosteal plate; epr, endosteal process; me, Meckel's cartilage; 



sa, sesamoid articular. 



