534 AMPHIBIA. 



three pieces, the largest an articular angulo-splenial, outside this a 

 thin dentary, and anteriorly uniting with its fellow a minute mento- 

 meckelian. 



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 lies 

 in the floor of the mouth and is produced into two anterior and two 

 posterior cornua. According to Villy, however, the columella is morpho- 

 logically connected with the ear capsule. 



The teeth are borne by the premaxillae, maxillae, and vomers. 

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

 distinct, and the pineal body is supposed to have been well de- 

 veloped. The foramen is also very distinct in some of the extinct 

 Ganoid Fishes. 



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 

 the suspensorium. In Elasmobranchs, the hyomandibular is the 

 suspensorium ; 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 Lepidostetts among Ganoids, or a hyoid and a palatoquadrate, 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 cartilaginous supra-scapula, and of 

 a ventral portion the coracoid, and the clavicle, and the 

 cartilaginous precoracoid on which the clavicle lies. There 

 is some uncertainty, however, in regard to the relations of 

 the last two ; according to one view, the clavicle is unrepre- 



