THE SESAMOID ARTICULAR 13 



Amiatus calva. 



Just above the posterior part of Meckel's cartilage are two small 

 bones in the typical position of the sesamoid articular. They were first 

 noticed by Bridge (Jour. Anat. Phys., vol. XI, 1877), who designated 

 them on his drawing of the mandible of Amiatus as "c" and "b" and so 

 referred to them without giving them names. To ossicle c is attached 

 a tendon from muscles that are probably homologous with parts of the 

 adductor mandibulae muscles in more highly specialized teleosts.* Dr. 

 Ridewood (Proc. Zool. Soc. Lond., 1904, p. 56) has failed to find these 

 two ossicles as separate bones and has homologized them with the endo- 

 articular. In two adult specimens I have at hand, however, these two 

 bones are very evident. Ossicle c is the sesamoid articular, and ossicle 

 b only represents the endoarticular. 



Polypterus bichir. 



In Polypterus I find no separate sesamoid articular, but on the inner 

 surface of the articular, just above Meckel's cartilage, in the typical place 

 for the sesamoid articular is a projecting shelf of bone to which a stout 

 adductor tendon is strongly attached. My only specimen is one 18 inches 

 in length. In the young I should confidently expect to find this process 

 as a separate sesamoid articular. 



Ceratodus forsteri. 



Of the lung-fishes I have only Ceratodus in which I find no sesamoid 

 articular. A big bundle of tendons gives muscle attachment to both the 

 ectoarticular and splenial just behind the mandibular tooth in the coro- 

 noid region. In the other lung-fishes there is no bone in published descrip- 

 tions or figures that could be homologized with the sesamoid articular. 



THE CLUPEOID FISHES. 



Dr. Ridewood, "On the Cranial Osteology of the Fishes of the Fami- 

 lies Elopidae and Albulidae" (Proc. Zool. Soc. Lond., 1904), reports the 

 sesamoid articular present in Elops saurus and in Albula vulpes, not 

 present in Pterothrissus gissu (Bathythrissa dorsalis), and in Me galops 

 cyprinoides he does not mention it, but he states that except for propor- 

 tions it resembles Elops. 



*For a discussion of these see Allis, Cranial Muscles and Nerves of Amia 

 calva. (Jour. Morph., XII, 1897, PP- 554, 5&) and 752.) 



