SKELETON OF FROG 



65s 



A delicate rod — the columella auris — extends from the tympanum 

 to the fenestra ovalis in the internal capsule of the ear. According 

 to Parker, it represents the upper part of the hyoid arch, the lower 

 portion of which forms the cartilaginous or partially ossified hyoid 

 plate, which hes in the floor of the mouth and is produced into two 

 anterior and two posterior cornua. 



The teeth are borne by the premaxillee, maxilla, and vomers. 



There is no parietal foramen, but in the Labyrinthodonts it is always 

 distinct. 



The cartilage which bears the quadrate at its lower end, and runs 

 between pterygoid and squamosal, connecting the articulation of the 

 lower jaw with the side of the skull at the auditory capsule, is called 



Fig. 376. — Pectoral girdle of Rana esculenta. — 

 After Ecker. 



The cartilaginous parts are dotted. Ep., Episternum ; om., omo- 

 sternum ; Ep.c, epicoracoids ; St., sternum ; x., xiphisternum ; 

 cL, clavicle with underlying precoracoid cartilage ; co., coracoid ; 

 Sc, scapula ; S.sc, supra-scapula ; Gl., glenoid cavity for humerus. 



the suspensorium. In Elasmobranchs the hyomandibular is the sus- 

 pensorium ; in Teleosteans the name is applied to the hyomandibular 

 and symplectic ; in Sauropsida the quadrate occasionally gets the same 

 confusing title. 



When the lower jaw is connected with the skull wholly by elements 

 of the hyoid arch, as in most Elasmobranchs and Ganoids, and all 

 Teleosteans, the term hyostylic is used. When the connection is due 

 to a quadrate element only, as in Dipnoi, Amphibia, and Sauropsida, it is 

 called autostylic. When there is both a hyoid and a quadrate element, 

 as in Lepidosteus among Ganoids, or a hyoid and a palato-quadrate, as 

 in Cestracion among Elasmobranchs and perhaps also in Holocephali, 

 the term amphistylic is used. Finally, it may be noted here tliat in 

 Mammals the lower jaw articulates with the squamosal. 



