Arcinella cornuta, or the Florida spiny jewelbox clam or Florida spiny jewel box, is a marine species of bivalve mollusc in the family Chamidae.

It can be found along the coast of North Carolina to Florida, Gulf of Mexico, Caribbean Central America, and Venezuela.

[1][2][3] The shell of A. cornuta is quadrangular to obliquely trigonal.

It attaches itself to surfaces during its early growth stage, after that it is free-living.

The shell features seven to nine radial rows of pleated radial ribs covered by large spines with coarse pitting between ribs.