horseshoe pitching, game played by two or more persons using horseshoes, the object being to throw the shoes so as to encircle a vertical iron peg that is 14 in. (35.6 cm) high. Regulation courts are at least 50 ft (15 m) long and 10 ft (3 m) wide; pitching distance is 40 ft (12.2 m) for men and 30 ft (9.1 m) for women. The tossing of quoits, metal, circular rings, with one rounded and one flat surface, is a related sport. Each ringer (horseshoe or quoit circling the peg) counts 3 points; each hobber, or leaner (horseshoe or quoit leaning against the peg), 2 points; and each horseshoe or quoit nearer the peg than that of the opponent, 1 point. A tally of 50 points wins at horseshoe pitching, while 21 points usually wins at quoits. At sea, the game of deck quoits is played, the quoits being made of rings of rope. Horseshoe and quoit pitching developed concurrently, and although their origins are obscure, they were both played in ancient Greece and Rome. The games were brought to England, where quoits attained great popularity. It is also popular in Ireland, Scotland, and Canada. Quoits was played in colonial America, but horseshoe pitching rapidly became more popular. The National Horseshoe Pitchers Association of America (organized 1914) conducts annual world's championships for men and women. Jukskei, a variant of horseshoe and quoit pitching, is played in South Africa.

horseshoe crab, large, primitive marine arthropod related to the spider, sometimes called a king crab (a name also used for the largest of the edible true crabs). The heavy dark brown exoskeleton, or carapace, is domed and shaped like a horseshoe. The body is divided into a broad, flattened, semicircular front part (the prosoma), a tapering middle part (the opisthosoma), and a pointed, spiky taillike part (the telson).

Horseshoe crabs have no jaws, and the mouth is flanked by a pair of pincerlike chelicera that are used to crush worms and other invertebrates taken as food. Five pairs of walking legs attached to the prosoma enable the animals to swim awkwardly or burrow through the sand or mud. The respiratory organs are called book gills and are unique to horseshoe crabs. Each book gill is made of about 100 thin leaves, or plates; these are fitted like pages of a book onto one pair of flaplike appendages on the opisthosoma. Rhythmic movement of the appendages circulates water over the gill surfaces and drives blood into and out of the gill leaves.

Horseshoe crabs first appeared in the Upper Silurian period, and a number of fossil species have been described. Five species still survive; four of these are found along the Pacific coast of Asia. The American species, Limulus polyphemus, is common along the Atlantic coast from Nova Scotia to Florida. It lives in shallow water, preferring soft or sandy bottoms, and reaches a maximum length of nearly 2 ft (61 cm).

Horseshoe crabs are considered living fossils; they resemble fossil trilobites and eurypterids of the Paleozoic era. They are classified in the phylum Chelicerata, class Merostomata.

horseshoe, narrow plate, commonly of iron or steel, shaped to fit a horse's hoof and attached to the hoof by nailing it to the inner edge of the horny wall of the hoof. Horseshoes vary from the light plate worn by race-horses to the heavy shoe with sharp pointed wedges, or calks, worn by horses of logging camps in drawing heavy loads over roads of ice. The earliest extant shoe dates from the 6th cent. B.C. A horseshoe used by the Romans was a leather boot with a metal plate at the bottom. Before the advent of motor vehicles, shoeing horses was an important trade, often combined with general blacksmithing. Often the horseshoer's skill cured lameness, and before veterinary medicine became a profession the horseshoer, or farrier, treated horses for all their diseases. The horseshoe is an emblem and talisman of good luck.

Horseshoe Bend, a turn on the Tallapoosa River, near Dadeville, E central Ala., site of a battle on Mar. 27, 1814, in which the Creeks, led by chief William Weatherford, were significantly defeated by a militia under the command of Andrew Jackson. As a result, large parts of Alabama and Georgia were subsequently opened to settlement. Horseshoe Bend National Military Park is there (see National Parks and Monuments, table).

Game for two or four players in which a horseshoe is thrown so as to encircle or land as close as possible to a stake. A horseshoe encircling the stake is called a ringer and counts for the highest score. The game may have derived from quoits, and it became especially popular in the U.S. and Canada. Regulation games are played to a winning score of 50, informal games to 21.

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Any of four extant species of marine arthropods (order Xiphosura, subphylum Chelicerata), found on the eastern coasts of Asia (three species) and North America (one species). Despite the name, horseshoe crabs are not crabs; they are more closely related to scorpions. Fossil relatives date back 505 million years. They are most abundant in estuarine waters. The North American species, Limulus polyphemus, can grow to more than 2 ft (60 cm) long. The body consists of three parts hinged together: a broad, horseshoe-shaped cephalothorax; a much smaller, segmented abdomen; and a long, sharp tail-spine, or telson. They spawn on sandy beaches in spring and summer. Adults feed on marine worms; larvae feed on small organisms.

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