''Bullia laevissima'',

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...

the fat plough shell, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...

, a marine

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Nassariidae The Nassariidae, Nassa mud snails (USA), or dog whelks (UK), are a taxonomic family of small to medium-sized sea snails, marine gastropod mollusks in the clade Neogastropoda. "Dog whelk" also refers to ''Nucella lapillus''. Shell description T ...

, the Nassa mud snails or dog whelks.

Description

The length of the shell varies between 35 mm and 67 mm. The smooth shell is ovate, oblong and ventricose. Its ground color is whitish with some slightly apparent, transverse-brown bands. The

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...

is reddish brown. The convex longitudinal folds are formed by the growth of the shell. The short

spire A spire is a tall, slender, pointed structure on top of a roof of a building or tower, especially at the summit of church steeples. A spire may have a square, circular, or polygonal plan, with a roughly conical or pyramidal shape. Spires are ...

is obtuse with sutures slightly apparent. The smooth

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An opt ...

is oblong and wide, narrowed at the upper part, somewhat more dilated at its base, where it is terminated by an oblique, wide emargination. The outer

lip The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...

is thin, rounded, colored internally of a fawn color. Externally, near the base, is observed a prominent fold, which is continued winding round as far as the inferior third of the

columella Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire. His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the wo ...

. This is arcuated, and slightly oblique. According to the observations of Quoy and Gaimard, the animal of this species is blind; and what renders it particularly remarkable, is a very large foot, extending from all parts of the shell. The operculum is exceedingly small. This mollusk possesses the power of absorbing by its foot, by means of pores with which this part is provided, a large quantity of water, which it throws off again, when it is disturbed, in several directions. It lives in deep water, and when it is brought towards the shore, its foot still farther enables it to bury itself in the sand. It is very voracious : it is generally taken, by placing a piece of flesh, as bait, in a net.Kiener (1840). General species and iconography of recent shells : comprising the Massena Museum, the collection of Lamarck, the collection of the Museum of Natural History, and the recent discoveries of travellers; Boston :W.D. Ticknor,1837
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Distribution

This marine species occurs off

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...

to South

Transkei Transkei (, meaning ''the area beyond he riverKei''), officially the Republic of Transkei ( xh, iRiphabliki yeTranskei), was an unrecognised state in the southeastern region of South Africa from 1976 to 1994. It was, along with Ciskei, a Ban ...

, South Africa

References

External links

* Marais J.P. & Kilburn R.N. (2010) Nassariidae. pp. 138–173, in: Marais A.P. & Seccombe A.D. (eds), ''Identification guide to the seashells of South Africa. Volume 1''. Groenkloof: Centre for Molluscan Studies. 376 pp * {{Taxonbar, from=Q4996913 Nassariidae Gastropods described in 1791