|Lucinidae, the lucinas, have shells that are circular, white or yellowish, with small centrally located beaks. There's usually a small ridge on the posterior end from the beak to the upper posterior margin. The shell may be smooth or have radial or concentric ridges or both. Lucinas usually live in soft mud or sand, in areas of low nutrients, low oxygen and high sulfide content. Sulfur-oxidizing bacteria in their gills also contribute to their nutrition. Lucinas have a long worm-like foot, that may be 6 times as long as the shell, that pushes through the substrate up to the surface. It is used to make a mucus-lined sandy tube used for water intake. The siphon for exhaling water retracts itself into the shells by inverting itself inside out. There are 11 species found in Texas.