Cardium Unido Shell Pairs These delicate bivalve shells whisper tales of ancient seas. Each Cardium unido pair, measuring 1 to 2 inches, carries the intricate ridged patterns that collectors and artisans cherish. Naturally formed and beautifully preserved, these matched shells showcase the ocean's geometric artistry—perfect for jewelry making, display collections, or crafting projects that celebrate marine heritage. Sold individually, each pair is a small treasure from the depths of aquatic history.