Bithyniidae is a family

Family

In human context, a family is a group of people affiliated by consanguinity, affinity, or co-residence. In most societies it is the principal institution for the socialization of children...

 of small freshwater snail

Freshwater snail

A freshwater snail is one kind of freshwater mollusc, the other kind being freshwater clams and mussels, i.e. freshwater bivalves. Specifically a freshwater snail is a gastropod that lives in a watery non-marine habitat. The majority of freshwater gastropods have a shell, with very few exceptions....

s with 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...

, 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 molluscs in the clade

Clade

A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 Littorinimorpha

Littorinimorpha

Littorinimorpha is a large clade of gastropods within Hypsogastropoda consisting primarily of marine species, but also aquatic and terrestrial species as well....

.

Their minute shell is often colored. They are characterized by a calcareous operculum, a lobe on the upper surface of the neck. The ctenidium

Ctenidium

Ctenidium may be:* Ctenidium , , a comb-like gill, part of the respiratory system of gastropods and bivalves* Ctenidium, , a row of peg-like spines in some insects...

, the respiratory gill-comb, is very broad. They have a ciliary feeding habit. The kidney has a large extension towards the mantle.

Genera

Genera in the family Bithyniidae include:

• Alocinna Annandale & Prashad, 1919
• Boreoelona Starobogatov & Streletzkaja, 1967
• Bithynia Leach, 1818 - type genus
  Type genus
  In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
  
  
  • Subgenus Bithynia Leach, 1818
  • Subgenus Codiella Locard, 1894
  • Subgenus Neumayria De Stefani, 1887
  • Subgenus Parafossarulus
    Parafossarulus
    Parafossarulus is a genus of freshwater snails with gills and an operculum, an aquatic prosobranch gastropod mollusks in the family Bithyniidae.- Species :Species within the genus Parafossarulus include:...
    
    Annandale, 1924
• Congodoma Mandahl-Barth, 1968
• Digoniostoma Annandale, 1920
• Funduella Mandahl-Barth, 1968
• Gabbia Tryon, 1865
• Gabbiella
  Gabbiella
  Gabbiella is a genus of small freshwater snails with an operculum, aquatic prosobranch gastropod mollusks in the family Bithyniidae.-Species:Species in the genus Gabbiella include:* Gabbiella balovalensis* Gabbiella humerosa...
  
  Mandahl-Barth, 1968
• Hydrobioides Nevill, 1884
• Incertihydrobia Verdcourt, 1958
• Jubaia Mandahl-Barth, 1968
• Limnitesta Mandahl-Barth, 1974
• Myosorella Annandale, 1919
• Pseudobithynia Glöer & Pešić, 2006
• Pseudovivipara Annandale, 1918
• Sierraia
  Sierraia
  Sierraia is a genus of freshwater snails with an operculum, aquatic prosobranch gastropod mollusks in the family Bithyniidae.-Species:Species in the genus Sierraia include:* Sierraia expansilabrum Brown, 1988 - vulnerable, from Sierra Leone...
  
  Conolly, 1929
• Tylopoma Brusina, 1882
• Wattebledia Crosse, 1886