72 / DR.. W. G, RIDEWOOD ON THE C'EANIAL [Mayo, 



of the ectosteal articular, and developecl above or around Meckel's 

 cartilage. This gives attachment to the tendon of a part of the 

 levator muscle of the mandible, and may be called the " sesamoid 

 articular," thus making a third component of the articular bone. 

 Vetter (Jena. Zeitschr. xii. 1878, pi. 13. fig, 8, iSs.) has called 

 attention to this bone in the Pike as a " Sesamoidverknocherung 

 an der Insertion der Endsehne von Ag — A^"^ an Meckel'schen 

 Knorpel," Ag being his third or deep portion of the adductor 

 mandibulse, and Ag' its tendon. 



This sesamoid aiticular is remarkably large in Albula (text-fig. 1 7, 

 p. 50), Gymnarchus, and Hyodon, in which it is set on theantero- 

 superior side of the endosteal aiticular. It is of fair size in 

 Notopterus^ Osteoglossuvi, and Gonorhynchus ; but as a rule it is 

 small, and is situated just in front of the endosteal articular 

 (e. g., Heterotis, Clupea), or at a short distance in advance of it 

 (e. g., Elops, Megalops). 



The sesamoid ai'ticular was described in 1878 in the mandible 

 of Eelone as a " coronoid bone" by Cope (Proc. Amer. Phil. Soc. 

 xvii. p. 695), who was of opinion that the bone occurred in no 

 family of Teleostean fishes except the Belonidfe. Gill, writing in 

 1895, described the bone in question as "lying mostly inside of 

 the upper portion of the dentary " (Proc. U.S. Nat. Mus. xviii. 

 1895, p. 173), and, admitting that it was not in any way homo- 

 logous with the coronoid of Lepidosteus, proposed to call it the 

 "addentary" (I.e. p. 174). The relation of this bone to the 

 dentary was, however, based upon an error on the part of Dr. Gill. 

 He writes (l. c. p. 173): — "This element appears to have been 

 unnoticed by most naturalists, and to have been first observed by 

 Dr. B. 0. Briihl. In 1847 Briihl (Anfangsgriinde der vergl. Anat. 

 aller Thierklassen, Atlas, pi. xi. fig. 17) published a figure of the 

 disintegrated light mandible in which the supplementary bone is 

 marked ZK. I have, however, been unable to find any reference 

 to it in the text." As a matter of fact, only two of the four bones 

 figured by Briihl are those of the mandible, the other two are 

 parts of the upper jaw, and are marked ZK and OK, which 

 abbreviations are explained on p. 88 of the text as standing for 

 ' Zwischenkiefer ' and ' Obei-kiefer ' respectively. 



The sesamoid aiticular has been minutely studied by Prof. 

 Starks, who in a letter to me dated March 15, 1904, states that it 

 is a small ossicle situated on the inner surface of the articular, 

 just above Meckel's cartilage, that it occurs at the loAver end of 

 the ligament (? tendon) which is attached to the articular, and 

 that it occurs much more commonly than is generally supposed. 

 In 1900 he published (Proc. U.S. Nat. Mus. xxii. 1900, p. 2, 

 footnote) a list of eighteen genera of Teleostean fishes in which 

 he had detected the presence of this " coronoid bone." 



Although teeth occupying the position of splenial teeth, and 

 referred to as such by Owen (Anat. of Vert. i. 1866, p. 123). 

 occur in the mandible of Arapaima, no separate splenial is to be 

 found in any of the fishes examined, which, being the lowest of- 



