46 GUIDEBOOK OF THE WESTERN UNITED STATES 
dipping succession of Coastal Plain formations, including a great 
thickness of strata of Tertiary age which have been penetrated by 
many deep borings. They are listed on page 50. Some of them 
yield artesian waters which supply flowing wells. The Lissie sand 
contains bones of animals of Pleistocene age, including the mastodon 
and mammoth, which have been found in gravel pits near Columbus. 
It is interesting to picture the assemblage of animals which ranged 
over this country a short time ago, in a geologic sense, and which are 
now entirely extinct. Many of them were very different from the 
animals of to-day, but were similar to animals found on other conti- 
nents. Notable among these were the large elephantlike mastodons 
and mammoths. The former (Mammut americanus), which was 
covered with long, coarse hair, ranged over a wide area, especially in 
the forested tracts. There were also mammoths of several species, 
notably Elephas columbi, which attained an average height of about 
11 feet, and Elephas imperator, which was considerably larger. They 
had huge curved tusks and teeth like those of modern elephants, with 
large grinding surfaces; apparently they lived on the open plains. 
Horses of several kinds and sizes were abundant, apparently ranging in 
immense herds over the wide interior plains, but after having persisted 
from a very remote period geologically they became entirely extinct 
here long before the coming of the Europeans with the modern horse. 
Tapirs were abundant in the south-central areas, and camels, wild 
hogs, and llamas were widely distributed. Deer and bison (buffalo) 
were plentiful, and some species of these have continued into the 
present era. The carnivores were varied and numerous, including the 
saber-toothed tiger, and some of these may have been contempora- 
neous with primitive man. Among the more curious-looking animals 
were the ground sloths, large unwieldy creatures covered with long 
hair and moving slowly, walking on the outer edge of their feet. 
Their enormous claws may have served for defense, but were very 
useful in dragging down branches of trees and digging roots and tubers. 
The Megalonyx, one variety of the sloth, was discovered and named 
by Thomas Jefferson, who was greatly interested in natural history. 
Another genus was Megatherium, which had a body as large as that of 
an elephant and much shorter legs. The genus Mylodon, smaller and 
lighter than the other genera, was common in part of the plains region. 
Giant armadillos existed in some parts of the region, and there was a 
great variety of rodents, reptiles, birds, and other animals, which have 
_ been replaced in large part by different genera and species. The 
modern armadillo, which abounds in part of central Texas, is shown in 
Plate 9, A. 
