204 DR. H. GADOW ON MEXICAN [June 6, 



for Newts during most of the Tertiary period : on the west the 

 plateau suffering from the volcanic revolutions ; on the east 

 the sea still covering the present Atlantic Tierra Caliente. The 

 Cretaceous parts formed so many oases where alone NeAvts could 

 exist or survive. Later, when the volcanic ranges, even the 

 volcanoes themselves, became covered with forests, the Newts 

 spread onto them, just as they have spread into the moist hot- 

 lands of the State of Yera Cruz. It may appear strange that the 

 limestone should have been the means of their preservation, con- 

 sidering that lime-water is, as a, rule, not favourable to their 

 development ; but here comes in the significant fact that most, if 

 not all, the Mexican Spelerpes are viviparous, unless they deposit 

 their eggs, like Batrachoseps, in hollow trees. Some of them, for 

 instance S. orizabensis, lead a partially arboreal life. We found 

 many on the pine-ti-ees of Citlaltepetl, favourite hunting and 

 hiding places being the epiphytic plants, especially the large 

 Tillandsias, Orchids, and Philodendron in the hot country forests. 

 The humus and moisture collecting in these growths, often many 

 feet above the ground, swarm Avith insect life and with little 

 Scolopendras, Avhich seem to be the staple food of these Speleiyes. 



The apparent absence of Newts on the Northern plateau is most 

 likely due to the dearth of permanent moisture, long-continued 

 periods of drought, and dust. A more difficult question is the 

 apparent absence of NeAvts on the teri'ain of gneiss and granite 

 which covers so large a portion of Southern Guerrero and Oaxaca, 

 and on the well-wooded moiuitains of the Sierra Madre. For 

 months have we searched Guerrero during the rainy season (there 

 are thousands of places Avhich, if they were on the Eastern slope, 

 would yield an abundance of NeAvts), but it was in vain. A few 

 specimens of S. belli, from the mountain forest of Omilteme, are 

 the only exception. 



Batraclioseps. — B. scuiatus ranges fi^om Illinois to Rhode Island 

 and to the Gulf of Mexico ; the other species live in the Pacific 

 States, from California to Oregon. Quite unexpected was there- 

 fore the occurrence of the Californian B. attenuatus on the NeA^ado 

 de Colima. I found a single, yoving specimen on the northern 

 slope, at about 7000 feet elevation, in the stump of a decayed pine- 

 tree. There are some patches of granite and of limestone in that 

 district, but then comes an unbroken stretch of originally 

 volcanic formation, for about 200 miles, until the gneiss is 

 reached to the north-east of Mazatlan. We cannot well imagine 

 that this species is an ancient surAdval ; it must be a comparatively 

 recent immigrant from the north-west, from California. Probably 

 it occurs all through the slopes of the western Sierra Madre, which 

 is mostly clad with pine-forests. 



Resume of the Distribution of Mexican Urodela. 



All the American Ui'odela are of Nearctic origin, Avith their 

 earliest centre in Old Sonoraland, At least the Amblysto- 



