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 maxillae, instead of being 

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

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

 tricts. Nearly allied is the single species of Pachijtriton, from South Kiansi, 

 China, in which the tail is cylindrical at the root, although compressed near 

 the tip. 



In the second sub-family Ambhjstomatince 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 vertebrae, too, 

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

 are slightly 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 Amblystvma tigrinum. It was long thought 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 single 

 outlying form in the mountains of 

 Siam. With the single exception of 

 the Mexican race of Ambiystoma 

 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 appears 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 Ambiystoma, 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 ~Lingucelapsus. A specimen 

 of L. annulatus has been taken in Arkansas from a hot spring.' Of the other 

 30 



Fig. 13. ADULT AXOLOTL 

 (Ambiystoma tigrinum). 



