68o PHYLUM CHORDATA : CLASS AMPHIBIA 



Family 3. Proteidae. — With persistent gills. Several species ol 

 Proteus inhabit the caves of Carinthia and Dalmatia. There 

 are two pairs of limbs. The eyes are degenerate and the skin 

 white, as we should expect in cave-animals. Two species of 

 Necturus (or M enobranchus) occur in N. American rivers and 

 lakes. 



Family 4. Sirenida?. — Two extant genera, Siren and Pseiidohranchus, 

 both N. American, both with persistent gills, and only 

 anterior limbs. Papillae in the lower dermic layer in Siren, 

 hidden by looser superficial dermis and epidermis, look like 

 vestiges of ancestral scales. 



'f^^ 



Order Gymnophiona or Apoda 



Worm-like or snake-like forms, subterranean in habit ; without 

 limbs or girdles ; with extremely short tail ; with dermic calcified 

 scales concealed in transverse rows in the skin ; in at least some forms 

 (Hypogeophis) external gills are present in the very young stages, but 

 disappear before hatching ; there may be no larval stage ; if there is, the 

 respiration is puhiionary. There are many other striking peculiarities : 

 — the eyes are small, covered up. and functionless ; there is no 

 tympanum or tympanic cavity ; there is a peculiar protrusible 

 tentacle in a pit behind the nostril ; there are only two pairs of 

 aortic arches (systemic and pulmonary). The notochord is largely 

 persistent ; the vertebras are amphicoelous ; the frontals are distinct 

 from the parietals ; the palatines are fused with the maxillae. The 

 eggs are large and meroblastic. They are altogether peculiar archaic 

 Amphibians. Examples : — Ccecilia (S. America) ; Ichthyophis (Ceylon), 

 India, Malay) ; Hypogeophis (E. Africa) ; Siphonops, without scales 

 (America). 



Order Stegocephali 



Extinct forms, occurring from Carboniferous to Triassic strata. 

 The earliest known digitate animals. 



Dermal armour is present, the teeth are frequently folded in a 

 complex manner (Labyrinthodonts). Mastodonsaurus, Dendrerpeton, 

 A rchegosaurus, Branchiosaurus. 



Life of Amphibians 



Most Amphibians live in or near fresh-water ponds, swamps, and 

 marshes. They are fatall}' sensitive to salt. Even those adults which 

 have lost all trace of gills are usually fond of water. The tree-toads, 

 such as Hyla, are usually arboreal in habit, while the Gymnophiona 

 and some toads are subterranean. 



The black salamander {Salamandra atra) of the Alps lives where 

 pools of water are scarce, and instead of bringing forth gilled young, 

 as its relative the spotted salamander (S. maculosa) does, bears them 

 as lung-breathers, and only a pair at a time. The unborn young have 



