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 Newts could 
exist or survive. Later, when the volcanic ranges, even the 
voleanoes themselves, became covered with forests, the Newts 
spread onto them, just as they have spread into the moist hot- 
lands of the State of Vera 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-trees of Citlaltepetl, favourite hunting and 
hiding places being the epiphytic plants, especially the large 
TMlndstne. Orchids, and Philodendron in the hot country forests. 
The humus and moisture collecting in these growths, often many 
feet above the ground, swarm with insect life and with little 
Scolopendras, which seem to be the staple food of these Spelerpes. 
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 Newts on the terrain of gneiss and granite 
which covers so large a portion of Southern Guerrero and Oaxaca, 
and on the well-wooded mountains of the Sierra Madre. For 
months have we searched Guerrero during the rainy season (there 
are thousands of places which, if they were on the Eastern slope, 
would yield an abundance of Newts), but it was in vain. A few 
specimens of S. belli, from the mountain forest of Omilteme, are 
the only exception. 
Batrachoseps.—B. scutatus ranges from 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 LB. attenwatus on the Nevado 
de Colima. I found a single, young 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 survival; 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. 
Résumé of the Distribution of Mexican Urodela. 
All the American Urodela are of Nearctie origin, with their 
earliest centre in Old Sonoraland. At least the Amblysto- 
