dient series is evident in which the
pikas and jack rabbits are the extremes. The black-tailed jack rabbit,
for example, in relation to size of the entire animal, has the longest
ears and longest hind legs. This kind of lagomorph takes alarm when an
enemy, for example, a coyote, is yet a long way off. The jack rabbit
seeks safety in running; even when being overtaken by a pursuer that is
close behind, the jack rabbit still relies on its running ability
instead of entering thick brush or a hole in the ground where its
larger-sized pursuer would be unable to follow. A cottontail has shorter
ears and shorter hind legs. It allows the enemy to approach more closely
than the jack rabbit does before running, and then, although relying in
some measure on its running ability for escape, flees to a burrow or
thicket for safety from its pursuer. The brush rabbit with ears and hind
legs shorter than those of the cottontail seldom if ever ventures
farther than 45 feet away from the edge of dense cover. After an enemy
is near, the brush rabbit has merely to scamper back into the brush.
Still shorter of ear and hind leg is the pigmy rabbit which ventures
outside its burrow to feed only among the tall and closely-spaced bushes
of sagebrush among which its burrow is dug. Detection of the slightest
movement of an enemy on the opposite side of the bush sends the pigmy
rabbit, in one or a few jumps, into the mouth of its burrow and, if
need be, below ground. The pika, with the shortest ears and legs of all,
lives in the rock slides and has to do little more than drop off the top
of a rock into a space between the broken rocks when an enemy is
detected near enough to the pika to have a chance of seizing it.

The number of molts in a year, depending on the kind of lagomorph,
varies in adults from one (according to Nelson, 1909:31) in the
cottontails (genus _Sylvilagus_) to as many as three (according to
Lyman, 1943, and Severaid, 1945) in the varying hare (_Lepus
americanus_). Difficulties that I have experienced in attempting to
account for the variations in color and wear of the pelage of the pika,
_Ochotona princeps_, on the basis of two molts per year, make me wonder
if it, too, has three molts. _Lepus townsendii_ certainly has at least
two molts per year.

KEY TO FAMILIES AND GENERA OF LAGOMORPHA

1. Hind legs scarcely larger than forelegs; hind foot less than 40;
nasals widest anteriorly; no supraorbital process on frontal