584 AMPHIBIA. 



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 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 that in 



Mammals the lower jaw articulates with the squamosal. 



The first or mandibular arch gives origin inferiorly to Meckel's 



cartilage, which forms the basis and persistent core of the lower 



jaw, and superiorly to the palato-pterygo-quadrate cartilage which 



is represented in the adult by the minute quadrate bone, by the 



suspensorial cartilage, and by other cartilages which are invested 



by the pterygoid and palatine bones. 



The second or hyoid arch gives origin inferiorly to the hyoid plate ; 



superiorly, according to Parker, to the columella. 

 Of the four posterior branchial arches, there are in the adult some 

 persistent remnants, e.g. in the larynx. 



The limbs and girdles. The shoulder-girdle consists of 

 a dorsal portion the scapula and the partially cartilagi- 

 nous supra-scapula, and of a ventral portion the coracoid 

 and the pre-coracoid. With the latter, according to most 

 authorities, a thin clavicle is associated. The glenoid 

 cavity, with which the humerus articulates, is formed by the 

 junction of scapula and coracoid. 



Between the median ends of the coracoids lie two fused 

 cartilaginous epicoracoids, behind which is a bony part of 

 the sternum, prolonged posteriorly into a notched cartila- 

 ginous xiphisternum. Anteriorly lies a bony portion called 

 the omosternum, which is prolonged forwards into an epi- 

 sternum cartilage. This sternum does not arise like that of 

 higher Vertebrates, from a fusion of the ventral ends of ribs. 

 Indeed, there are no ribs in the frog, unless they be minute 

 rudiments at the ends of the transverse processes. 



The true frogs (Ranidse) have what is called a firmisternal pectoral 

 arch, in which precoracoid and coracoid nearly abut on the middle line, 

 and are only narrowly separated by the epicoracoids. In toads, tree-frogs, 

 etc., the arch is arciferal, the precoracoid and coracoid being widely 

 separated medianly, and connected by a large arched epicoracoid, over- 

 lapping its fellow. 



The skeleton of the fore-limb consists of an upper arm 



