Triviella millardi 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...

 of small sea snail

Sea snail

Sea snail is a common name for those snails that normally live in saltwater, marine gastropod molluscs....

, a 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...

 gastropod mollusc in the 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...

 Triviidae

Triviidae

Triviidae is a taxonomic family of small sea snails, marine gastropod molluscs in the clade Littorinimorpha.-Taxonomy:The following subfamilies were recognized in the taxonomy of Bouchet & Rocroi in 2005:*Eratoinae Gill, 1871**tribe Eratoini Gill, 1871...

, the trivias.

Distribution

This snail is known around the South African coast from Port Nolloth

Port Nolloth

Port Nolloth is a town and domestic seaport in the Namaqualand region on the northwestern coast of South Africa, 89 miles northwest of Springbok....

 to the Cape Peninsula

Cape Peninsula

The Cape Peninsula is a generally rocky peninsula that juts out for 75 km into the Atlantic Ocean at the south-western extremity of the African continent. At the southern end of the peninsula are Cape Point and the Cape of Good Hope...

 in 10-30 m. It is endemic to that area.

Description

Triviella millardi has a plump round white shell

Gastropod shell

The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...

, which is usually completely covered with the yellowish mantle

Mantle (mollusc)

The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.In many, but by no means all, species of molluscs, the epidermis of the mantle secretes...

, which is variably streaked with white or may have dark spots. It reaches a maximum size of 40 mm.

Ecology

The white-streaked form of this animal resembles the scribbled nudibranch

Scribbled nudibranch

The scribbled nudibranch, Doriopsilla miniata, is a species of sea slug, a dorid nudibranch. It is a marine gastropod mollusc in the family Dendrodorididae.-Distribution:This species is known from the Mediterranean, and the Indo-Pacific...

, Doriopsilla miniata, which may cause fish predators to avoid it.