THE SESAMOID ARTICULAR 15 



The sesamoid articular is a very large, thick bone closely attached 

 to the front of the endosteal part of the articular, with its outer surface 

 against the ectosteal part. Its surface is almost as great as that of the 

 endosteal part, and has the appearance of being in as close relationship 

 with Meckel's cartilage. Its structure, its union with Meckel's cartilage, 

 and its concave lower edge, from which the cartilage issues, are all strik- 

 ingly like the endosteal part. 



Dorosoma cepedianum. 



Dr. Ridewood reported on Dorosoma erebi, and did not mention a 

 sesamoid articular or show one in his picture. This species has a well 

 developed one in front of the cup-shaped process of the endosteal part 

 of the articular, and partly covered by Meckel's cartilage. 



Dussumieria elopsoides. 



Dr. Ridewood reports the sesamoid missing in Dussumieria acuta, but 

 in this species there is a small one situated against the articular and partly 

 covered by Meckel's cartilage. 



Clupea pallasii. 



Dr. Ridewood reports the sesamoid articular missing in Clupea 

 harangulus. In this closely related species it is present, situated against 

 the articular just in front of the endosteal process, and covered by the 

 base of Meckel's cartilage. 



Opisthonema oglinum. 



The sesamoid articular is moderately large, and is situated on the 

 upper part of Meckel's cartilage and the endosteal process. 



Coilia nasus. 



In this form Dr. Ridewood failed to find a sesamoid articular. A 

 small one is present, however, in the deep notch that is formed directly in 

 front of the articulating surface of the quadrate, and covered by Meckel's 

 cartilage. The line of demarcation between the endosteal and ectosteal 

 parts of the articular is not evident. 



