Leodia sexiesperforata Flat Sea Urchin Sand Dollar Sea Hedgehog Echinoderma Echinozoa Echinoidea Irregularia Mellitidae

Leodia sexiesperforata Flat Sea Urchin Sand Dollar cm 7.5-8.5  Sea Hedgehog Echinoderma Echinozoa Echinoidea Irregularia Clypeasteroida Mellitidae.
Family: Mellitidae.
Common name: Sand Dollar or The Six-Holed Keyhole Urchin.
Syn. Echinodiscus sexiesperforatus, Echinus hexaporus, Leodia richardsonii, Mellita erythraea, Mellita hexapora, Mellita platensis, Mellita sexforis, Mellita similis, Scutella hexapora, Scutella sexforis.

Leodia sexiesperforata, commonly known as the six-keyhole hedgehog, is a species of sand dollar, of the order clipeasteroid echinoderms. It is native to tropical and subtropical areas of the western Atlantic Ocean from North Carolina south to Uruguay.
Like other sand dollars, Leodia sexiesperforata is radially symmetric and dorsoventrally flattened, with a circular or semipentagonal shape, but also exhibits secondary bilateral, front-to-back symmetry. It is usually between 4.8 and 14.5 cm (1.9 and 5.7 in) in diameter. The mouth is located on the oral (lower) surface and is surrounded by the peristome and five deep narrow alimentary grooves, which branch as they approach the margin. On the aboral (upper) surface of the hedgehog there are five small petal-like areas which are used as gills and six oval lunules (slits) which give the species its name "sexiesperforata". Five of these fissures are found in the ambulacral areas and the sixth is in the posterior interambulacral area. The anus is located in this lunula.
The aboral surface is slightly domed, the highest point being on the anterior petal, while the oral surface is flat. The surface of the body is covered with small spines which give it a velvety appearance. The color of this sand dollar varies, but is usually a shade of yellowish brown or tan, sometimes white.
It is found at depths of up to about 60 m (200 ft) but is most common at less than half that depth. It inhabits sandy bottom areas where there is little algae growth and buries itself in soft sediment to a depth of about 2.5 cm. It can bury itself in five or seven minutes. The purpose of the lunulae may be to equalize the pressure above and below the sand dollar, thereby reducing lift and helping to prevent it from being swept away by strong currents. It feeds on debris and small organic particles, collecting them with the tubular pedicels on the oral surface, moving them into the food grooves and from there into the mouth, where they are ground by the teeth.