THE SAND DOLLAR.....................................

SAND DOLLAR..............................................

SHELLS ON THE BEACH.......................

SEA URCHIN.................

SAND DOLLARS ARE FLAT,

ROUND MARINE ANIMALS, RELATED TO SEA URCHINS, AND SEA STARS. THE MOST COMMON SAND DOLLAR IS WIDESPREAD IN OCEAN WATERS OF THE NORTHERN HEMISPHERE, FROM THE ZONE TO CONSIDERABLE DEPTHS.

THE SAND DOLLAR HAS A RIGID SKELETON KNOWN AS A TEST. WHEN SAND DOLLARS ARE LIVING, THEY HAVE A SKIN OF MOTILE SPINES COVERING THE TEST. MOVEMENT IS ACCOMPLISHED BY THE COORDINATED ACTION OF THE SPINE. LIKE SEA URCHINS, SAND DOLLARS HAVE FINE PAIRED ROWS OF PORES. IN SAND DOLLARS THEY ARE ARRANGED IN A PETAL-LIKE PATTERN. THESE PORES ARE PERFORATIONS IN THE ENDOSKELETON, THROUGH WHICH THE PODIA USED IN GAS EXCHANGE PROJECT, FROM THE BODY.

THE SAND DOLLAR LIVE BEYOND LOW WATER, ON TOP OR JUST BENEATH THE SURFACE OF SANDY OR MUDDY AREAS. ON THE OCEAN BOTTOM, SAND DOLLARS ARE FOUND TOGETHER. THIS IS BECAUSE THEY LIKE SOFT AREAS, WHICH ARE CONVENIENT FOR THEIR REPRODUCTION. THE SEXES ARE SEPARATED, AND AS WITH MOST ECHINOIDS, GAMETES ARE RELEASED INTO THE WATER COLUMN. THEY ARE CONCEIVED BY EXTERNAL FERTILIZATION AS WITH MOST ECHINOIDS. LIVE SAND DOLLARS CAN BE GREENISH, BLUISH, OR PURPLE. THEIR HIGHLY MODIFIED SPINES AND PODIA GIVE THEM A VELVET LIKE TEXTURE AND APPEARANCE.