NEWTS AND SALAMANDERS. 449 



Islands, constitute a genus confined to the Oriental region, and differing from 

 all those mentioned above in the conformation of the skull in which the 

 pterygoid bones extend forwards to touch the maxillie, instead of being 

 separated from them by an interval. These salamanders have five hind-toes 

 and tlie tail strongly compressed. They are inhabitants of mountain dis- 

 tricts. Nearly al led is the single species of PachytHton, from South Kiansi 

 China, m which the tail is cyUndrical at the root, although compressed near 

 the tip. o i 



In the second sub-family — ^mfeZysfomaimfe — of the Salamandridce the 

 teeth on the palate form either a transverse or posteriorly converging series, 

 and are attached to the hinder margin of the posterior portion" of the 

 vomers, instead of to processes of the palatine bones. The vertebrse, too, 

 differ from those of the first group in that both terminal faces of their bodies 

 are sHghtly cupped ; this being a lower type of structure than the ball-and- 

 socket articulation. The type of this group is the creature known in Mexico 

 as the axolotl, which is the permanent larval form of a salamander from the 

 United States described as AvMystoma tirjrhium. It was long thout^ht that 

 these two forms were totally distinct 

 animals ; but the identity of the two 

 was conclusively proved by some 

 Mexican axolotls kept many years 

 ago in Paris. One of these layed 

 eggs, which in due course developed 

 into axolotls, but these latter ulti- 

 mately assumed the form of the 

 adult salamander. The most curious 

 fact about the matter was that where- 

 as the axolotls bred freely, none of 

 the adult salamanders could be in- 

 duced to propagate their kind. There 

 are several species of the genus in- 

 habiting North America, and a suigle 

 • outlying form in the mountains of pig^ 13. -Adult Axolotl 



Siam. With the single exception of (AmUijstomatigrmum). 



the Mexican race of Ainblystcmia 



tigrinum, all these appear to pass from the tadpole to the salamander stage 

 in the usual manner. The reason of the Mexican race retaining the larval 

 stage ajjpears to be that the country is very arid, and unfit for amphibian 

 life. Consequently the axolotls remain permanently in the, large lake by 

 which the city of Mexico is surrounded. In this larval condition they have 

 a long compressed tail, with a crest above and below, which is continued as 

 a ridge on the back ; and on the sides of the neck are abundant bushy 

 external gills. The limbs are rather small, and the general hue of the skin 

 is mottled olive. On the other hand, the adult — which is normally developed 

 in the United States — is an ordinary-looking salamander, with a relatively 

 large head, good-sized limbs, and a sub-cylindrical tail ; the colour of the 

 skin being blackish or brown, with numerous yellow spots. As special 

 characteristics of the genus Amhhjstoma, it may be mentioned that the teeth 

 on the palatines are arranged either in nearly a straight line or in an angle 

 without any wide gap in the middle, and that the tongue bears a series of 

 radiating pleats. Very closely allied is the genus Lingiicdapsus. A specimen 

 of L, anmdatus has been taken in Arkansas from a hot spring.- Of the other 

 80 



