North American beaver large, webbed hind feet. The unwebbed front paws are smaller, with claws. The eyes are covered by a nictitating membrane which allows the beaver to see under water. The nostrils and ears are sealed while submerged. A thick layer of fat under its skin insulates the beaver from its coldwater environment. The beaver's fur consists of long, coarse outer hairs and short, fine inner hairs (see Double coat). The fur has a range of colors, but usually is dark brown. Scent glands near the genitals secrete an oily substance known as castoreum, which the beaver uses to waterproof its fur.
Castor and Pollux represented in the Circus Maximus by the use of eggs as lap counters. In translations of comedies by Plautus, women generally swear by Castor, and men by Pollux; this is exemplified by the slave-woman character Staphyla in "A Pot of Gold" (act i, ll.67–71) where she swears by Castor in line 67, then the negative prefix in line 71 denotes a refutation against swearing by Pollux. The Etruscans venerated the twins as "Kastur" and "Pultuce", collectively the "tinas cliniiaras", "sons of Tinia," the Etruscan counterpart of Zeus. They were often portrayed on Etruscan mirrors. As was the fashion in Greece,