sand dollar

sand dollar (plural sand dollars)

1. Any echinoderm of the order Clypeasteroida, having a flat, disk-shaped body with the mouth in a mid-ventral position, and living in sand, on or near the surface.
   • 1987, John M. Lawrence, chapter I, in A Functional Biology of Echinoderms‎, page 75:

     In the sand dollars, the arrangement of the food grooves and consequently the lateral water vessels and their accessory tube feet is more complex (Phelan 1977).

   • 2000, Sandra Alters, chapter I, in Biology: Understanding Life‎, page 692:

     Adult echinoderms have a five-part body plan corresponding to the arms of a sea star or the design on the "shell" of a sand dollar.

   • 2001, Jennifer Hahn, Spirited Waters: Soloing South Through the Inside Passage, 2009, page 135,

     If you look carefully, a sand dollar is merely a sea urchin in flattened form.

• (any species of Clypeasteroida): clypeasteroid