4 THE SESAMOID ARTICULAR 



to its identity. He called it the Operculaire (number 37 of his picture), 

 homologizing it with a bone in the jaw of reptiles that he called by the 

 same name, supposing the reptile bone homologous with the true opercle 

 bone of fishes, though in the fish he also uses this name (number 28) for 

 the bone commonly so called. 



In 1846 Owen, in his Lectures on Comparative Anatomy and Physi- 

 ology of the Vertebrates, published a picture of the mandible of the Sudis, 

 Arapiama gigas, with the following remarks: "The great Sudis and 

 the Polypterus have the splint-like plate along the inner surface of the 

 ramus, answering to that which Camper and Cuvier have unfortunately 

 called 'operculaire' in the mandible of reptiles, but to which I have given 

 the name of 'splenial' to prevent the confusion from the synonymy with 

 the true opercular bone of fishes." Later in his Comparative Anatomy 

 Owen included Amiatus with the other two forms, and adds : the splenial 

 "supports teeth and develops a coronoid process." 



It thus appears that Owen's splenial is the bone that usually bears 

 that name in the Ganoids. It need scarcely be added that no homology 

 exists between the splenial, which is clearly a dental cement bone, and 

 the sesamoid articular (Cuvier's Operculaire). 



Giinther, in his Introduction to the Study of Fishes (p. 91), makes 

 a similar mistake when he refers to the os operculare as a synonym of the 

 splenial as follows. "The splenial or os operculare, which is situated on 

 the inside of the articulary." 



Ridewood (Linn. Soc. Jour., XXIX, p. 267), in writing of the 

 mandible of the Sudis, says: "Although the bony lamina that bears the 

 teeth occupies the position of the splenial bone, it is not a distinct plate 

 of bone as might be concluded from the remark of Owen." There can 

 be little question but that Owen referred to this inseparable toothed plate, 

 rather than to a sesamoid articular. Dr. Ridewood reports the sesamoid 

 articular not present. 



Owen, in a table of synonyms that he published in his Lectures, 

 includes the name subvomeral of Geoffrey St. Hilaire. I fail to find the 

 term in the paper Owen cites (Ann. des. Sci. Nat., Ill, 1824), and there- 

 fore can not be sure whether it is the homolog of the sesamoid articular 

 or of the splenial; but if of the former it is an earlier account of the 

 bone than the one given by Cuvier. 



Agassiz also uses the term Operculaire for the splenial of Polypterus 

 and Lepisosteus (Poissons Fossiles, vol. 2, part 2, pp. 20 and 42, pi. B 

 and C, 1843), but in the Sudis (Piscium Brasiliensium, pi. B, 1829) he 

 applies operculaire to an entirely different bone, that Owen in the same 



