452 AMPHIBIA ORDER II. C A UDA TA. 



According to the system of classification now favoured by zoologists, the 



tailed amphibians constitute a series regularly descending in their grade of 



organisation ; and with the present family we reach a group 



Family in which the external gills of the young are permanently 



Proteidce. retained, while there are two pairs of rudimental limbs. An 



additional peculiarity is to be found in the absence of the 



maxilla in the scull. As in the preceding family, the bodies of the vertebrae 



.have cupped terminal faces, and eyelids are wanting. The typical member 



of the family is the famous olm (Proteus) from the subterranean waters 



of Carniola, Carinthia, and Dalmatia. No better description of this creature 



is extant than one by Sir Humphry Davy, which runs as follows: "At 



first sight you might suppose this 

 creature to be a lizard, but it has the 

 motions of a fish. Its head and the 

 lower part of its body and its tail 

 bear a strong resemblance to those 

 of an eel ; but it has no fins ; and its 

 curious bronchial organs are not like 

 the gills of fishes ; they form a 

 singular vascular structure, almost 

 like a crest round the throat, which 

 may be removed without occasioning 

 Fig. 15. OLM (Proteus anguineus). the death of the animal, which is like- 



wise furnished with lungs. With 



this double apparatus for supplying air to the blood, it can live either below 

 or above the surface of the water. Its fore-feet resemble hands, but they 

 have only three claws or fingers, and are too feeble to be of use in grasping 

 or supporting the weight of the animal. The hinder feet have only two 

 claws or toes, and in the larger specimens are found so imperfect as to be 

 almost obliterated. It has small points in place of eyes, as if to preserve the 

 analogy of nature. It is of a fleshy whiteness and transparency in its natural 

 state, but when exposed to light, its skin gradually becomes darker, and at 

 last gains an olive tint. Its nasal organs appear large ; and it is abundantly 

 furnished with teeth, from which it may be concluded that it is an animal of 

 prey ; yet in its confined state it has never been known to eat, and it has 

 been kept alive for many years by occasionally changing the water in which 

 it was kept." From the olm the North American genus Necturus is at 

 once distinguished by the possession of well-developed eyes, and likewise by 

 the presence of four toes to each foot. In form, too, it is more lizard-like, 

 the body lacking the eel-like elongation characteristic of the olm, while the 

 limbs are less rudimental. There are two species of the genus, one of which 

 is not uncommon in the rice-fields of the Southern United States. Although 

 both breathe almost entirely by means of their plume-like external gills, it 

 is stated that they will occasionally venture on land, when the lungs of 

 course become the respiratory organs. In sinking a well recently in Texas, a 

 third generic representative of the family was discovered at a depth of 180 

 feet in a subterranean stream. This form is related both to Proteus and 

 Necturus, and has been named Typhlomolge rathbuni. It is characterised by 

 the great length and slenderness of its limbs, and the broad, flattened, and 

 squared muzzle. 



The last family of the tailed amphibians is confined to North America, 

 where it is represented by Siren lacertina of the South-Eastern United 



