# Velutinidae

Velutinidae is a family of small sea snails, marine gastropod molluscs in the clade Littorinimorpha.

## Description

The length of the shell varies between 25 m mand 40 mm.
The shell of these animals is very thin and delicate, and internal, completely covered by the mantle (which has fused lobes) so the appearance of these animals more closely resembles that of dorid sea slugs rather than sea snails, but anatomically quite different. They are readily distinguished by the anterior siphon and typically snail-like, tentacle-bearing head beneath the anterior mantle. There are no rhinophores (chemosensory tentacles) or dorsal circlet of gills.
The shell is present but is completely internal. It is covered by a fleshy mantle. The ventral surface features a distinct foot and a head bearing tentacles with basal eyes. The anterior of the dorsal surface (notum) is indented along the midline, forming a short siphon. The mantle is relatively firm but has a somewhat gelatinous texture, appearing mostly smooth. The internal shell resembles an ear, being thin and fragile.
The colour is translucent, greyish-white to pinkish or yellow with black/brown spots and blotches. This colouration is variable, resembling that of the ascidian prey on which they live and feed and thus providing camouflage.

## Taxonomy

The following two subfamilies were recognized in the taxonomy of Bouchet & Rocroi (2005):
* Subfamily Velutininae J. E. Gray, 1840 - synonyms: Marseniidae Leach in Gray, 1847; Marsenininae Odhner, 1913; Capulacmaeinae Golikov & Gulbin, 1990; Onchidiopsinae Golikov & Gulbin, 1990 (n.a.); Marseniopsidae Badel, 1993 (n.a.)
* Subfamily Lamellariinae A. D. d'Orbigny, 1841 - synonyms: Coriocellidae Troschel, 1848; Sacculidae Thiele, 1929 (inv.); Pseudosacculidae Kuroda, 1933
| Drawing of dorsal view of live animal of Lamellaria latens | Drawing of ventral view of live animal of Lamellaria latens |

## Genera

Genera within the family Velutinidae include:
* Calyptoconcha
** Calyptoconcha pellucida A. E. Verrill, 1880 - translucent lamellaria
* Cartilagovelutina Golikov & Gulbin, 1990
** Cartilagovelutina beringensis (Derjugin, 1950)
** Cartilagovelutina chondrina (Bartsch in Derjugin, 1950)
** Cartilagovelutina cristata (Derjugin, 1950)
* Ciliatovelutina Golikov & Gulbin, 1990
* Cilifera Golikov & Gulbin, 1990
* Coriocella Blainville, 1824
* Echinospira Krohn, 1853
* Lamellaria G. Montagu, 1815
* Lamellariopsis Vayssière, 1906
* Limneria H. Adams & A. Adams, 1851
* Marseniella Bergh, 1886
** Marseniella borealis Bergh, 1886
* Marsenina Gray, 1850
* Marseniopsis Bergh, 1886
* Mysticoncha Allan, 1936
* Onchidiopsis Bergh, 1853
** Onchidiopsis glacialis M. Sars, 1851 - icy lamellaria
** Onchidiopsis latissima Odhner, 1913
** Onchidiopsis spitzbergensis Jensen, in Thorson, 1944
* Piliscus Lovén, 1859
** Piliscus commodus Middendorff, 1851
** Piliscus rostratus (Golikov & Gulbin, 1990)
** Piliscus undulatus (Golikov & Gulbin, 1990)
* Pseudosacculus Hirase, 1928
* Pseudotorellia Warén, 1989
** Pseudotorellia fragilis Warén, 1989
* Torellivelutina McLean, 2000
* Velutina Fleming, 1820
** Velutina plicatilis (Müller, 1776)
** Velutina schneideri Friele, 1886
** Velutina velutina (Müller, 1776)
Subfamily Lamellariinae A. D. d'Orbigny, 1841
Subfamily Velutininae Gray, 1840

### Genera brought into synonymy

* Capulacmaea M. Sars, 1859 : synonym of Piliscus Lovén, 1859
* Chelinotus Swainson, 1840: synonym of Coriocella Blainville, 1824
* Cryptocella H. Adams & A. Adams, 1853: synonym of Lamellaria Montagu, 1815
* Marsenia Oken, 1823: synonym of Lamellaria Montagu, 1815
* Marvillia [sic]: synonym of Limneria H. Adams & A. Adams, 1851
* Morvillia Gray, 1857: synonym of Limneria H. Adams & A. Adams, 1851
* Oithonella Mörch, 1857: synonym of Marsenina Gray, 1850
* Oncidiopsis [sic]: synonym of Onchidiopsis Bergh, 1853
* Pilidium Middendorff, 1851: synonym of Piliscus Lovén, 1859
* Pseudoacculus [sic]: synonym of Pseudosacculus Hirase, 1928
* Sacculus Hirase, 1927: synonym of Pseudosacculus Hirase, 1928
* Velutella Gray, 1847: synonym of Velutina Fleming, 1820