THE SESAMOID ARTICULAR 27 



THE RHEGNOPTERI. 



Polydactylus approximans. 



In this form the endosteal process stands away from the ectosteal 

 plate (inward from it), and a flat bridge of bone projects upward from 

 it to near the edge of the ectosteal plate just in front of the condyle for 

 the quadrate. The cavity behind it (outward from it) is doubtless the 

 homolog of the chamber in the mandible of Elops in the same region, 

 where it is completely separated as a chamber rather than simply bridged 

 across. As the partition in Elops unquestionably belongs to the ectosteal 

 part of the articular, it probably does here, though it is so completely 

 anchylosed with the endosteal process that its boundary is obscure. The 

 sesamoid articular is situated in the space between the endosteal process 

 and the ectosteal plate. Its middle is opposite the end of the process, and 

 it is equally in contact with the process and Meckel's cartilage, which 

 entirely hide it as the mandible is viewed from the side. 



THE BERYCOID FISHES. 



Beryx splendens, Hoplostethus japonicus, Monocentris japonicus, 



Polymixia japonica. 



In these forms the sesamoid articular is against the ectosteal plate 

 on the outer side, and the endosteal process and Meckel's cartilage on the 

 inner. Viewed from the side, the process and cartilage hide it from view. 

 In Hoplostethus it is rather flat and disk-like. In Beryx it is a thick, 

 elongate splint of bone with a tubercle at its middle for the attachment of 

 the tendon. In Polymixia and Monocentris it is very small but thick. 

 In Monocentris it is very loosely attached. 



Holocentrus ascencionis, Myripristis occidentalis. 



These two forms are similar in the condition of the sesamoid articu- 

 lar. It is of moderate size, situated against the ectosteal plate just in 

 front of the endosteal process, and on its lower edge folding over the top 

 of Meckel's cartilage. 



THE SCOMBRID^E. 



Scomber japonicus, Scomberomorus sierra, Sarda chilensis, Gymno- 

 sarda palamis, Acanthocybium solandri. 



In all of these the sesamoid articular is rather small, situated on 



