THE ENDOSKELETON 



691 



Fig. 410. 



A, Dorsal and B, Ventral views of cranium of Branchiosaurus aalamandr aides, 

 C, Posterior view of cranium of Trematosaurus. Br, branchial arches ; C, condyle ; 

 Ep, epiotic ; F, frontal ; J, Jugal ; L.O, lateral occipital ; M, maxillary ; N, nasal ; 

 No, nostril ; Pa, parietal ; PI, palatine ; Pm, premaxillary ; P.o, postorbital ; Pr.f, 

 prefrontal ; Pa, parasphenoid ; Pt, pterygoid ; Ptf, postf rental ; Q, quadrate ; Qj, 

 quadrate- jugal ; S.o, supraoccipital ; Sq, squamosal ; St, Supratemporal ; V, vomer. 

 (After Gadow.) 



D, Chondrocranium of a frog shortly after metamorphosis. fov, fenestra 

 vestibuli ; m, Meckel's cartilage ; mtg, metapterygoid ; nc, nasal capsule ; ptgq, 

 pterygoquadrate ; tnas, tectum nasalis ; tsyn, tectum synoticum ; timed, taenia 

 tecti medialis ; III- V, nerve exits. (From Kingsley after Gaupp.) 



subsidiary to the sense of hearing or it may be lost, the question not be- 

 ing decided. The hyoid proper becomes more or less intimately con- 

 nected with the arches behind and also is largely concerned in affording 

 a support for the tongue. 



"The branchial arches are all similar to each other in the lower ver- 

 tebrates, but with the loss of branchial respiration in the higher groups, 

 they tend to become reduced, the reduction beginning behind. Some may 

 entirely disappear, others give rise to the laryngeal cartilages and the 

 first may fuse with the hyoid. The first arch is in the region of the ninth 

 nerve ; the others in that supplied by the tenth." 



*Here it will be necessary to review the frog skull very thoroughly', 

 bearing in mind that, as in all vertebrates, the occipitals, the two sets of 



"The frog does not have all the bones mentioned. All head bones that any vertebrate pos- 

 sesses are given in the list, so that the student must not expect to find any animal with all these 

 structures, though he will find no vertebrate with head-bones not mentioned here. 



