Coquina is the Spanish word for cockleshells or shellfish. Coquina forms near shore, where wave action is vigorous and sorts the sediments well. Most limestones have some fossils in them, and many have beds of shell hash, but coquina is the extreme version. A well-cemented, strong version of coquina is called coquinite. A similar rock, composed chiefly of shelly fossils that lived where they sit, unbroken and unabraded, is called a coquinoid limestone. That kind of rock is called autochthonous (aw-TOCK-thenus), meaning "arising from here." Coquina is made of fragments that arose elsewhere, so it is allochthonous (al-LOCK-thenus). Those are handy words in geology.