Hydromylidae is a taxonomic 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 sea slug

Slug

Slug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...

s, 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...

 opisthobranch gastropod mollusks in the suborder Gymnosomata, the sea angel

Sea angel

Sea angels previously known as one kind of pteropod, are a large group of small swimming sea slugs in six different families. These are pelagic marine opisthobranch gastropod molluscs in the clade Gymnosomata within the larger clade Heterobranchia....

s.

Hydromyles species are pelagic, carnivorous and viviparous.

Description

The small pelagic snails of the family Hydromylidae lack a shell (except in their early embryo

Embryo

An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

nic stage). They are carnivores, equipped with swimming parapoda (fleshy, winglike outgrowths), strong jaws and grasping tentacles, often with suckers resembling those of cephalopod

Cephalopod

A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

s.

A more comprehensive discussion can be found under the entry sea angel

Sea angel

Sea angels previously known as one kind of pteropod, are a large group of small swimming sea slugs in six different families. These are pelagic marine opisthobranch gastropod molluscs in the clade Gymnosomata within the larger clade Heterobranchia....

.

Genera and species

Genera and species within the family Hydromylidae include:
Genus Hydromyles

Hydromyles

Hydromyles is a taxonomic genus of small sea slugs, marine opisthobranch gastropod mollusks in the family Hydromylidae. They are sometimes known as sea angels.Hydromyles species are pelagic, carnivorous and viviparous....

Gistl, 1848

• Hydromyles globulosus (Rang, 1825)
  • Distribution: East Pacific, North America
    North America
    North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
    
    , western Atlantic.
  • Description: This pteropod seizes its prey with its radula
    Radula
    The radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...
    
    . Contrary to most gymnosomatiids, this pteropod has no proboscis and no hooks. It is also unique by having, close to the anal aperture, a sac for hatching its eggs. The larva
    Larva
    A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
    
    e develop in this sac and are born as fully developed snails. In other words this species is viviparous.