164 CHORD ATA. 



Class III. Amphibia. 



Cold-blooded Vertebrates with naked glandular skin, a sacral ver- 

 tebra, and (generally) paired limbs, consisting of girdle with free limb 

 transversely divided into three regions/ A cloaca, lungs, temporary 

 or permanent branchial respiration, and an incomplete double circula- 

 tion. Median fins, when present, not supported by tin-rays. Amnion 

 absent, and allantois represented by a urinary bladder. Frequently a 

 metamorphosis. 



Order 1. Urodela (Caudata), tailed forms. 



Ichthyoidea, notochord largely persistent, and vertebrae bicon- 

 cave : Proteus anguineus, in the underground streams of Carniolu ; 

 Siredon pisciformis, Axolotl, may lose its gills (becoming Ambly- 

 stoma); both preceding perennibranch. Menopoma, and Sieboldia 

 (Cryptobranchus) Japonicus, lose their gills (caducibranch), but retain 

 a pair of gill-clefts. 



Salamandrina (Myctodera), adults without gills or gill-clefts; 

 vertebra} opisthoccelous. Triton cristatus, great water newt, with 

 spermatheca, oviparous. Salamandra maculosa, viviparous. 



Order 2. Batrachia (Anura). With elongated hind-limbs, and 9-11 

 procoelous vertebrae. Tail, gills, and gill-slits only present in the larva. 

 Pipa dorsigera, female with brood- pouches on the back. Eana escu- 

 lenta, edible frog, R, temporaria, common frog, R. oxyrhinus. Bom- 

 binator igneus. Bufo vulgaris, toad. Hyla arborea, tree-frog, toes 

 with suckers. 



Order 3. Apoda (Gymnophiona). Serpent-shaped subterranean forms 

 devoid of limbs, tail, gills, and gill-clefts. Skin with small dermal scales ; 

 vertebra* amphicrelous. Co3cilia lumbricoidea. Epicrium. Sipho- 

 nops. 



Order 4. Steyocephali. Extinct forms, often of large size, with tail, 

 dermal armour, and well-ossified pubes. Carboniferous to Trias. 

 Labyrinthodon. 



