|Tellinidae, the tellins, have shells that are round to oblong in shape and are usually thin and flattened. The anterior end is rounded, and the posterior end is more elongate. Their surfaces are usually smooth but may have fine concentric or radial ridges. Tellins bury themselves, usually lying horizontally on their left valve which allows the right valve to become more inflated. They extend their siphons up through the mud to the surface to suck up edible bits while they remain safely buried. Tellin clams also have hemoglobin which give the animal a bright red color. They are important as food sources and, because of the coloration on some of the shells, in shell collecting. There are 25 species found in Texas waters.