Glycymerididae, previously known as Glycymeridae, common names dog cockles or bittersweets, is a worldwide family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of marine

Marine (ocean)

Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...

 bivalve mollusks, related to the ark clam

Ark clam

Ark clam is the common name for a family of small to large-sized saltwater clams or marine bivalve molluscs in the family Arcidae. Ark clams vary both in shape and size. They number about 200 species worldwide....

s. In this family the shell is generally round in outline, is slightly longer than it is wide, and the external ligament lacks transverse striation

Striation

Striations means a series of ridges, furrows or linear marks, and are used in several ways* Glacial striation* Striation , a striation as a result of a geological fault* In medicine, striated muscle...

s. The shell in some genera is smooth and in others is ribbed. This family contains 45 species in four genera.
The name of the family was originally Glycymeridae when it was established in 1916.