98 Frerp Museum or NatuRAL History — Zoétocy, Vor. XI. 
less herbivorous and many of them are practically omnivorous. Of 
the large number of families belonging to this great order, 10 are rep- 
resented in North America, of which 7 occur within our limits. 
KEY TO THE SUBORDERS AND FAMILIES. 
GROUP 1. Upper incisors 2 (Suborder SIMPLICIDENTATA), p. 98. 
SECTION 1. Body largely covered with sharp, stiff spines or quills partly 
concealed by fur. Family ERETHIZONTID&. 
American Porcupines, p. 253. 
SECTION 2. Body not largely covered with sharp quills. 
Parr 1. Tail broad, flattened (paddle shaped), naked, and scaly; size large. 
Family CASTORIDA. Beavers, p. 158. 
Part 2. Tail not broad, flattened and paddle shaped. 
A. Hind legs and feet noticeable elongated (kangaroo-like). 
Tail very long; size small (about that of a Mouse). 
Family ZAPODIDZ. Jumping Mice, p. 246. 
B. Hind legs and feet ordinary, not greatly elongated. 
br. Tail closely or scantily haired or naked. 
Claws of fore feet not greatly elongated; no external cheek pouches. 
Family MURIDZE. Rats, Mice, etc., p. 171, 
Claws of fore feet greatly elongated; external cheek pouches 
present. Family GEOMYIDZ. Pocket Gophers, p. 239. 
bz. Tail thickly haired and more or less bushy. 
Family SCIURID. Squirrels, Woodchucks, etc., p. 98. 
GROUP 2. Upper incisors 4, the second pair much smaller and placed behind the 
front pair. (Suborder DUPLICIDENTATA), p. 258. 
Ears long; hind legs long. Family LEPORIDA. Hares and Rabbits, p. 259. 
Suborder SIMPLICIDENTATA. 
Family SCIURIDA. Squirrels, Woodchucks, 
etc. 
The Sciuride are a highly specialized and widely distributed family, 
being cosmopolitan with the exception of the Australian region. Some 
exotic species are highly colored, showing much red, orange and yellow. 
They vary in size from the diminutive S. soricinus of Borneo, which 
is about the size of a Mouse, to the Malayan species, S. bicolor, which 
is as large asa Cat. A cecum is always present, which in most of our 
species will average from one-seventh to one-ninth the length of the 
large intestine. 
Those which occur within our limits differ greatly in form and 
