''Maxwellia gemma'', commonly known as gem murex, is a species of

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 in the family Muricidae, the murex snails or rock snails.

Description

The

fusiform Fusiform means having a spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon-shape, but often implies a focal broadening of a structure that continues from one or both ends, such as an aneurysm on a b ...

shell is of moderate size and its length varies between 16 mm and 40 mm. The color of the shell is somewhat white with spiral bands with a reddish-brown to bluish-black color on the leading edge of each varix. The shell has a rather short, subacute, conical spire. There are five convex

whorls A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). Whorls in nature File:Photograph and axial plane floral d ...

. The

body whorl The body whorl is part of the morphology of the shell in those gastropod mollusks that possess a coiled shell. The term is also sometimes used in a similar way to describe the shell of a cephalopod mollusk. In gastropods In gastropods, the b ...

is broad and spindle-shaped. Each spire whorl contains six rounded varices that are broader at the

, but thinner and curved back at the stubby, top whorls and around the

siphonal canal The siphonal canal is an anatomical feature of the shells of certain groups of sea snails within the clade Neogastropoda. Some sea marine gastropods have a soft tubular anterior extension of the mantle called a siphon through which water is ...

. The sutures between the whorls are deep and crossed by the oblique varices. The porcelaneous white aperture has an oval shape and has a finely dentate outer lip. The siphonal canal is rather short, almost completely closed and curved to the left at the base. There is no apparent anal canal. The inner surface of the aperture has a rippled form, reflecting the form of the ribs at the outer surface. The columella is smooth.George E. Radwin,Anthony D'Attilio, ''Murex shells of the world: an illustrated guide to the Muricidae'', p. 154
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Distribution

This species is distributed in the Pacific Ocean along California to Central Baja California, Mexico in rocky areas from the littoral zone to depths of 55 m. It can often be found in great numbers on

breakwater Breakwater may refer to: * Breakwater (structure), a structure for protecting a beach or harbour Places * Breakwater, Victoria, a suburb of Geelong, Victoria, Australia * Breakwater Island Breakwater Island () is a small island in the Palme ...

s and close to the entrances to bays.

References

External links

* Muricopsinae Gastropods described in 1879 {{Muricopsinae-stub