Two quarter horses.
quarter horse definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
any of a breed of light, muscular horse of a solid, usually dark color: because of its quick reactions it is much used in Western range work and in rodeos
Origin: after its great sprinting speed at a quarter of a mile
quarter horse definition by American Heritage Dictionary
One of a breed of strong saddle horses developed in the western United States.
Origin: From its formerly being trained for races up to a quarter mile.