304 



ZOOLOGY 



SECT. 



Fig. 052.— Pelvic girdle of Salamandra. «, !>, 



processes of epipubis ; i?/). epipubis ; Fo. ob- 

 tiinitiir foramen ; G. acetabulum ; II. ilium ; 

 y.s'. i.schiiun ; P. pubis ; Sjj. pubo-iscliiatic sym- 

 physis ; *, processes of pubis present in some 

 Urodeles. (From Wiedcrsheim.) 



the einimhis {Ep). It is developed independently of the pelvis, and 

 its relations to that structure are very similar to those of the 



sternum to the shoulder-girdle; 

 it lias, in fact, been proposed 

 to call it a, 2}clvi-ster7ium. 



The limbs of TJrodela differ 

 from the typical structure 

 already described only in de- 

 tails : there are usually four 

 digits in the fore-limb and 

 five in the hind-limb. In 

 Anura the limbs are modified 

 by the fusion of the radius 

 and ulna and of the tibia and 

 fibula, and by the great 

 elongation of the two proximal 

 tarsals. A prehallux is fre- 

 quently present. 



Myology. — In the lower 

 Urodela the muscles of the 

 trunk and tail occur in the 

 form of typical myomeres like 

 those of Fishes. In tlie 

 higher forms the myomeres become converted into longitudinal 

 dorsal bands — the extensors of the hack, paired ventral bands — the 

 recti abdominis, and a double layer of oblique muscles, covering the 

 flanks. 



Digestive Organs. — -The teeth are always small and ankylosed 

 to the bones : they may be singly or doubly pointed. They occur 

 most commonly on the premaxillse, maxilke, and vomers, but may 

 also be developed on the dentaries, palatines, and, in one instance, 

 on the parasphenoid. In many Anura, such as the Common 

 Toad, teeth are altogether absent. In some of the Stegocephala, 

 such as 3Iastodonsauri's, the teeth are extraordinarily complex in 

 structure, the tissues being folded in such a -way as to produce in 

 section a complex tree-like pattern. It is from this circumstance 

 that the term Labyrinthodont, often applied to the Stegocephala, is 

 derived. 



The enteric canal is divisible into buccal cavity, pharynx, gullet, 

 stomach, small intestine, rectum, and cloaca. The stomach and 

 duodenum together form a U-shaped loop in which the pancreas 

 lies. The tongue in many Urodeles is fixed and immovable, like 

 that of a Fish : in most Anura it is free behind, as in the Frog ; 

 but in Xonopus and Pipa (hence called Aglossa) it is absent. 



Respiratory Organs. — With very few exceptions Amphibia 

 possess external gills in the larval state, and, in the perenni- 

 branchiate Urodela, these organs are retained throughout life. 



