''Pleurotomella normalis'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

, a marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Raphitomidae Raphitomidae is a Family (biology), family of small to medium-sized sea snails, marine (ocean), marine gastropod mollusks in the superfamily Conoidea.Bouchet P. & Rocroi J.-P. (Ed.) (2005). "Classification and nomenclator of gastropod families" ...

Description

(Original description) The short and very stout shell contains seven

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). In nature File:Photograph and axial plane floral diagra ...

s. The

body whorl The body whorl is part of the morphology (biology), morphology of the gastropod shell, 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 ...

measures about eight elevenths of the whole length. The apex of the

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 " ...

is smooth. The remainder consists of the 3½ yellow-brown nuclear whorls, beautifully reticulated with wavy transverse lines, then changing suddenly into waxy white. The subsequent whorls show spiral threads, set in pairs which frequently blend to make one flattened spiral thread, with wider interspaces between the threads. Two or three threads next the suture are stronger and wider apart than the others, the outer one strongest, giving the whorl a turreted appearance, and rising into little knobs on the transverse ridges. These ridges are rather sharp, sixteen to eighteen in number, fading away toward 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 i ...

in most but not all specimens, flexuous with the lines of growth. The

columella Lucius Junius Moderatus Columella (, Arabic: ) was a prominent Roman writer on agriculture in the Roman Empire. His in twelve volumes has been completely preserved and forms an important source on Roman agriculture and ancient Roman cuisin ...

is straight, the edge obliquely cut off, shorter than the

aperture In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...

anteriorly. There is a light deposit of callus on the body. The aperture is proportionally wide, thin-lipped and about half as long as the shell. Bulletin of the Museum of Comparative Zoology at Harvard College v 9-11 (1881-1885)

Distribution

This marine species occurs in the Yucatan Strait.

References

* de Boury, E., 1899. Révision des pleurotomes éocènes du Bassin de Paris. La Feuille des Jeunes Naturalistes 29: 117-163, sér. 3° série

External links

Holotype at MNHN, Paris
* {{DEFAULTSORT:Pleurotomella Normalis normalis Gastropods described in 1881