IV. VERTEBRATA: AMPHIBIA, 



515 



articular portion, like the quadrate, being rarely incompjletely ossified. Vomers, 

 palatines, and pterygoids appear in the base of the skull, all three forming a 

 continuous arch in the Anura; in front of them lie the premaxillaries, and in 

 most cases maxillaries. Between the hinder end of the maxillaries and the 

 quadrate there may be a gap or it may be bridged by a jugal. By the modifica- 



J' "f JT 



Fig. 566. — Lateral and hinder views of frog skull fafter Parker). Letters for 

 this and 565: qh, angulare; As, alisphenoid cartilage; co (Cocc), occipital condyles; 

 col, columella; d, dentary; E (e), sphenethmoid; fo, foramen magnum; FP, fronto- 

 parietal; Gk, otic capsule; h', h", hyoid and copula; jg, jugal; M (m), maxillary (in 

 lower jaw mento-Meckelian); mk, Meckel's cartilage; N, TV', nasal capsule; na, nasal; 

 oh, OS, cartilages from which basi- and supraoccipitals arise elsewhere; ol (Olat), e.xoc- 

 cipital; pf, frontoparietal; Pal, palatine; p (PP), palatine arch; Pmx, prema.xiUary; Pro, 

 prootic; Ps, parasphenoid; Pt, pterygoid; Qu, quadrate; Qjg, jugal; sq, squamosal; Vo, 

 vomer. Cartilages dotted. 



tion of the quadrate into a suspensor the hyomandibular loses its function, and 

 if represented at all, it is as part of the columella. The character of the remain- 

 ing visceral skeleton depends upon the respiration (fig. 567). Where gills 

 occur, the copula and hyoids — representing body and cornua — as well as four 

 gill arches are present, but with pulmonary respiration the hyoid apparatus is 

 reduced to a hyoid with anterior and poste- 

 rior cornua, the gill arches being contained 

 in the posterior horns. To understand the 

 conditions in the higher vertebrates it must 

 be remembered that the reduced fifth arch 

 becomes a support of the larynx and that in 

 many anura the hyoid extends to the skull 

 and fuses with the otic capsule. 



With the assumption of a terrestrial 

 life changes occur in the sense organs. 

 The organs of the lateral line, which 

 occur in all larvje and are persistent in 

 the aquatic perennibranchs, and the 

 nerves which supply them, disappear; the eyes in the Salamandrina have 

 upper and lower lids; in the frogs an mider lid (really nictitating mem- 

 brane). The nose becomes respiratory and is provided with choanas 

 opening into the mouth. Especially noteworthy is the auditory appa- 

 ratus. This, in the urodeles and cjecilians, is very primitive, even the 

 tympanum being absent, but in the Anura a sound-conducting appa- 



FiG. 567. — Hinder visceral skele- 

 ton of (.1) larva of a salamander; 

 (B) of toad (from Gegenbaur). o, 

 body of hyoid; b, anterior horn 

 (hyoid); c, rest of branchial skeleton. 



