582 



CHORD AT A. 



(dentary, splenial, angulare, etc.); its articular portion, like the 

 quadrate, being rarely incompletely 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 premaxil- 



fo. os. 



FIG. 612. Lateral and hinder views of frog skull. (After Parker.) Letters for this 

 and 611 : an, angulare ; As, alisphenoid cartilage; co (Cocc), occipital condyles; 

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

 frontoparietal; Gk, otic capsule: h',h", hyoid and copula; jg, jugal; M (m), 

 maxillary (in lower jaw mento-Meckelian) ; ink, Meckel's cartilage; N, N l , 

 nasal capsule; na, nasal; ofo, os, cartilages from which basi- and supraoccipitals 

 arise elsewhere ; ol (Olcrt), exoccipital ; p/, frontoparietal ; Pal, palatine ; p (PP), 

 palatine arch; Pmx, premaxillary ; Pro, prootic; Ps, parasphenoid: Pt, pterygoid; 

 Qw, quadrate; Qjg, jugal; s</, squamosal; Fo, vomer. Cartilages dotted. 



laries, 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 modification 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 remaining vis- 

 ceral skeleton depends upon the 

 respiration (fig. 613). Where gills 

 occur, the copula and hyoids repre- 

 FTG. 613. Hinder visceral skeleton of sentingr body and cornua as well as 



(A) larva of a salamander ; (B) of 



toad. (From Gegenbaur.) a, body lour gill arches are present, but with 



of hyoid; fo, anterior horn (hyoid); _ . 



c, rest of branchial skeleton. pulmonary respiration the hyoid ap- 



paratus is reduced to a hyoid with anterior and posterior cornua, 

 the gill arches being contained in the posterior horns. 



With the assumption of a terrestrial life changes occur in the 

 sense organs. The organs of the lateral line, which occur in all 

 larvae 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 under lid (really nicti- 

 tating membrane). The nose becomes respiratory and is provided 

 with choanse opening into the mouth. Especially noteworthy is 

 the auditory apparatus. This, in the urodeles and caecilians, is 



