Limpets & Keyhole Limpets Approximately 35 species of limpets live in North American waters. Raised or low conical shells may be smooth or ribbed, round or narrow at the base, and may reach 4 inches in diameter. Limpets living in more turbulent wave areas have lower shell heights than those living in calmer conditions. Limpets living among seaweed or grasses have longer, narrower shells.
Keyhole limpets have a hole or slit near the apex of their conical shell that sets them apart from true limpets. North American waters contain 102 species of this gastropod.
