The anchialine pool snail, scientific name Neritilia hawaiiensis, is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 living in brackish estuaries and in anchialine pools. These snails have an operculum

Operculum (gastropod)

The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...

, and are aquatic

Aquatic animal

An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...

 gastropod mollusk in the family Neritiliidae

Neritiliidae

Neritiliidae is a family of submarine cave snails, marine gastropod mollusks or micromollusks in the clade Cycloneritimorpha...

.

Distribution

This species is endemic to the islands of Hawaii

Hawaii

Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

, United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, and lives only in brackish estuaries and in anchialine pools, which are marine pools that have no surface connection with the ocean but that are salty and that fluctuate in level with the tides.