THE SESAMOID ARTICULAR 



37 



Gadus callarias, Pollachius brandti. 



A small part of Meckel's cartilage is replaced by the sesamoid articu- 

 lar and the cartilage is unossified before and behind it. The outer part 

 of the ossification spreads out in a broad plate of bone over the ectosteal 

 plate, where it is firmly attached. This outer part resembles the sesamoid 

 articular as found in many forms. A stout tendon is attached to a rather 

 wide base formed by both the part replacing cartilage and the part against 

 the ectosteal plate. The endosteal process is ossified on the surface only, 

 for a considerable space at its anterior end leaving cartilage within. 



epr 



Fig. 15. GADUS CALLARIAS 



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

 cartilage; sa, sesamoid articular. 



THE HETEROSOMATA. 



Psettichthys melanostictus, Eopsetta jordani, Parophrys vetulus, 

 Citharichthys sordidus. 



The sesamoid articular is against the ectosteal plate directly in front 

 of the endosteal process, and covered more or less by Meckel's cartilage. 

 In Parophrys it is larger than in the others and more disk-like. 



Usinosita japonica. 



The endosteal process is scarcely developed, and the endosteal part 

 of the articular consists of little more than enough bone to form the 

 concavity for the articulation of the condyle of the quadrate. Articulated 

 to this bone directly in front of the concavity is a large sesamoid articular 

 which rests broadly on Meckel's cartilage. 



