24 THE SESAMOID ARTICULAR 



the endosteal process, extending forward over the posterior end of 

 Meckel's cartilage. Upward and backward it projects above the articu- 

 lar in a process that shows to a considerable extent when viewing the 

 mandible from the outer surface. To it the muscle is closely attached 

 by tendinous tissue, as herein described under adductor muscles. It is 

 of such a size and position that it is little wonder Cope called it the coro- 

 noid, though it is considerably behind the coronoid bone of reptiles, or 

 the coronoid cartilage of Amiatus. The anterior upper angle of the 

 articular of Tylosurus, which is just behind the dentary, is in the coro- 

 noid region. 



Fig. ii. TYLOSURUS ACUS 



an, angular; d, dentary; ecpl, ectosteal plate; me, Meckel's cartilage; 

 sa, sesamoid articular. 



Exocoetus californicus. 



The sesamoid articular is here as it is in Tylosunts, except that it 

 scarcely extends above the articular to be visible from the outside. 



Chirodorus atherinoides, Hemiramphus richardi. 



These forms have the sesamoid articular essentially alike and almost 

 identical with that of Tylosurus. 



THE HEMIBRANCHIATE FISHES. 

 Gasterosteus cataphractus. 



In this form the sesamoid articular is 'a nodule of bone on the upper 

 part of Meckel's cartilage attached against the ectosteal plate of the 

 articular far from the coronoid region, or the upper margin of the man- 

 dible. It is smaller than in the other Hemibranchiate fishes. 



