''Gymnobela xylona'' 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 Raphitomidae
Raphitomidae is a family of small to medium-sized sea snails, marine gastropod mollusks in the superfamily Conoidea.Bouchet P. & Rocroi J.-P. (Ed.) (2005). "Classification and nomenclator of gastropod families". '' Malacologia'' 47(1-2). . 3 ...
.
Description
The length of the shell attains 27 mm, its diameter 12 mm.
(Original description) The thin, white shell is elongate and subturrited. It contains eight
whorl
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 ...
s beside the (lost)
protoconch
A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also called ...
. The deep suture is distinct and not channelle. The whorl in front of it slopes flatly to an angular shoulder and is sculptured with three or four flattish spiral threads with slightly wider interspaces separated from the keel at the shoulder by a channel three times as wide as the others. The shoulder keel is duplex, the posterior cord most prominent, the anterior, closely adjacent, less so. In front of these, extending to 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 ...
, is a series (five on the penultimate whorl, eighteen on 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 ...
) of similar but less prominent, subequal, and subequidistant cords, with numerous smaller intercalary threads, the interspaces wider than the primary cords. From the shoulder to the periphery on the body whorl are (on the type species about fourteen) numerous obscure narrow vertical riblets extending to but not over the base, but not nodulating the superincumbent cords. There are also numerous very fine, slightly prominent growth lines which tend to roughen the spiral
sculpture. The
aperture is short and wide. The outer
lip (defective) is thin and simple. The body, with the sculpture erased, is polished, milky white. The
columella is very short, gyrate, almost pervious. The siphonal canal is very short and wide.
W.H. Dall (1908) Reports on the Mollusca and Brachiopoda, Bulletin of the Museum of Comparative Zoology at Harvard College. vol. 43
(described as ''Pleurotomella xylona'')
Distribution
This marine species was found off the Galapagos Islands at a depth of 2,487 m.
References
External links
*
Gastropods.com: ''Gymnobela xylona''
{{DEFAULTSORT:Gymnobela Xylona
xylona
Gastropods described in 1908