i8 



THE SESAMOID ARTICULAR 



and extends into the cavity of the dentary sheath along the top of Meckel's 

 cartilage. The dentary sheath is wide open behind, unlike that of Lepto- 

 cephalus conger. 



Ophichthus triserialis, Ophisurus serpens, Lycodontis castaneus. 



In these forms the sesamoid articular and its relationship to the sur- 

 rounding elements differ in no important way from that of Muraenesox. 



Fig. 6. LYCODONTIS CASTANEUS 

 d, dentary; epl, ectosteal plate; epr, endosteal process; sa, sesamoid articular. 



THE HETEROGNATHOUS FISHES. 

 Hoplias microlepis. 



The sesamoid articular is a thick, irregular bone on top of Meckel's 

 cartilage, and attached against the articular just anterior to the endo- 

 steal process of that bone. The tendon is slender. 



Curimatus isognathus. 



In this the sesamoid articular is placed as in Hoplias, but the bone 

 is thinner and flatter and fits more broadly on the articular. 



Hydrocynus cuvieri. 



The sesamoid is a flat bone with a tubercle for the attachment of the 

 tendon. It lies closely against the ectosteal part of the articular on top 

 of Meckel's cartilage and the endosteal process. 



