Ancient Indian belief classifies the conch into male and female varieties. The thicker-shelled bulbous one is thought to be the male (purusha), and the thin-shelled slender conch to be the female (shankhini).
The fourfold caste division is also applied as follows:
a). The smooth white conch represents the Brahmin caste
b). The red conch the kshatriyas (warriors)
c). The yellow conch the vaishyas (merchants)
d). The grey conch the shudras (labourers)
Additionally, there is a fundamental classification of conch shells occurring in nature: those that turn to the left and those which turn to the right.
Shells which spiral to the right in a clockwise direction are a rarity and are considered especially sacred. The right-spiralling movement of such a conch is believed to echo the celestial motion of the sun, moon, planets and stars across the heavens. The hair whorls on Buddha's head spiral to the right, as do his fine body hairs, the long curl between his eyebrows (urna), and also the conch-like swirl of his navel.
Vajrayana Buddhism absorbed the conch as a symbol which fearlessly proclaimed the truth of the dharma. Among the eight symbols, it stands for the fame of the Buddha's teaching, which spreads in all directions like the sound of the conch trumpet.
In addition to Buddha's throat, the conch also appears as an auspicious mark on the soles, palms, limbs, breast or forehead of a divinely endowed being.
This article by Nitin Kumar