The sculpture of this shell of Epitonium scalare is raised vertical ribs which are known as costae. Costae are a common feature in the shells of many species within the genus Epitonium, generally known as wentletraps (a word derived from the Dutch word for spiral staircase). This wentletrap species is particularly large, and the costae are exceptionally well developed; they are in fact the only structure that joins the whorls of the shell together.
This shell was greatly prized in Europe during the 17th and 18th centuries. The shell is still known as the "precious wentletrap", even though it no longer commands high prices from shell collectors.
The pulmonate land snail Cepaea hortensis crawling up a twig. Because the shell is somewhat translucent in this species, the presence of the pallial lung is noticeable as a relatively large light area showing the volume of air within the mantle cavity.
The muscles that pull back the ommatophores (the two upper tentacles, which have eye spots at the ends) are lightly pigmented, and are visible as two parallel lines that reach through the base of the tentacles and back into the body. Part of the tail protrudes below the shell at the end of the animal. Land snails of this size (shell about 2 cm) can climb vertical surfaces and even hang upside down when necessary.
In this image, the different internal organ systems of the animal are shown in artificial colors in order to be easier to view and understand. The mass which is colored green near the tip of the animal's visceral hump is the digestive gland. The black dot with the notation "ey" at the head end marks the position of the right eye. "f" marks the foot.
The snail Indrella ampulla from a tropical rainforest habitat in India. The shell in this species is reduced: the body cannot be fully retracted into the shell. The mantle is partly visible here as an area of off-white color under the edge of the shell. The rest of the body (head with retractile tentacles and most of the foot) is red. The foot fringe is off-white, with narrow black lines. The large caudal mucous pit is visible at the end of the foot.
The shell of the Venus comb murexMurex pecten has an extremely long siphonal canal. The shell has over one hundred spines, which provide protection from predation, and prevent the snail from sinking in the soft mud. This image shows three views of one shell: an apertural view on the right, abapertural view on the left, and apical view at the bottom.
This species is commonly known as the "orange peel doris" because of its striking coloration, which is an example of aposematism. The bright orange color serves as a warning signal to potential predators because this nudibranch is toxic. When it is handled, it gives off a chemical which smells like sandalwood.
The California sea hare can sometimes grow to be as large as 75 cm in length, measured when actively crawling. It is a herbivore, and feeds mostly on red algae. This species has become a valuable laboratory animal for the study of neurobiology.
This is one of the most problematic invasive species in the world. It has been accidentally or deliberately introduced to many other areas of the world, where it now represents a very serious threat to agriculture, to native ecosystems, and also to local snails as a food competitor.
The flesh of this species is edible, and in the Western world it is sometimes kept as a pet, but it is under strict quarantine in some countries, (for example the USA), where keeping it as a pet is illegal because of the danger of accidental introduction into the wild.
These snails belong to the family Planorbidae, the ramshorn snails, which are known for their planispiral, left-coiled shells, for having the red blood pigment hemoglobin, and also as intermediate hosts for various parasites, including medically important ones.
The Spanish slugArion vulgaris (still often incorrectly referred to as Arion lusitanicus) is a large land slug with a body length of up to 12 cm. It is brown in color. This is a highly invasive species and is considered to be the worst European agricultural pest. It belongs to the family Arionidae, the roundback slugs. Species in this family of slugs have the respiratory opening or pneumostome positioned just anterior to the mid-point of the mantle. The pneumostome is visible in this image as a circular opening behind the head on the right-hand side of the slug. The shell of the Spanish slug is completely reduced, existing only as internal microscopic calcareous granules.
The individual in this image has paused and is rearing up, perhaps to investigate its surroundings. Normally the front part of the foot of the animal is kept on the substrate.
This sea hare has a small and soft internal shell that is made of conchiolin. The two horn-like or ear-like structures on the top of the head (which cause the resting animal to slightly resemble a hare or rabbit) are the rhinophores, which are used primarily for chemoreception.
This unusual sea slug, the pelagicaeolidnudibranchGlaucus atlanticus, also known as the "sea swallow" has a flattened body with rayed cerata and dark blue stripes along the edge of its foot. This sea slug lives floating upside down at the surface of the water, as shown here from above. Its body is dark and pale blue ventrally (the upper surface as it floats), and silvery grey on its true dorsal side.
This species typically grows to 6 cm in length, and it feeds on medusas, including venomous ones, and also on other pelagic gastropods. Because this sea slug concentrates the stinging power of the medusas, it can deliver a very painful and somewhat dangerous sting to humans.
An apertural view of a shell of the small, air-breathing, freshwater snail Physella acuta in the family Physidae. This an example of a sinistral or left-handed shell, which means that if the shell is held with the aperture facing the observer, and the spire pointing up, then the aperture is on the left-hand side. In this genus the aperture is long and large, and the spire is pointed. The shell is thin and corneous, and rather transparent.
The family Physidae and the family Planorbidae are within the superfamily Planorboidea; all the species within these families have shells that are left-handed. In general however, sinistral shell coiling is quite rare among the gastropods.
An apertural view of an adult shell of the extremely large sea snail known as the Australian trumpet, Syrinx aruanus in the family Turbinellidae. This species is the largest Recent shelled gastropod species; the height of the shell can be up to 91 cm.
The shell itself is usually pale apricot in color as shown here, however in life the shell is covered by thick brown or grey periostracum. The whole shell has a spindle-like shape and the spire of the shell is quite high. The whorls usually have a strong keel and the shell has a long siphonal canal. There are no folds on the columella, unlike some other genera within the same family.
In this image, a rod is visible protruding from the siphonal canal; this metal structure is used to support the specimen as it is on display in the Houston Museum of Natural Science.
A representation of the external and internal anatomy of a common air-breathing land snail such as Helix aspersa. Air-breathing land snails have a well-defined head with two or four sensorytentacles with eyes at the tips of the upper pair, a ventral foot, and a shell. The viscera are grouped in a hump that is contained within the spiral shell.
Four different views of the same shell of the land snail Arianta arbustorum: apertural view (top left) showing its aperture; lateral view (top right); apical view (bottom left) showing its apex and umbilical view (bottom right).
The video shows the Spanish slug, Arion vulgaris, opening its pneumostome (breathing pore), which is on the right side of its body, in front of the mid-point of the mantle. The pneumostome opens into an internal space that functions as a pallial lung. This space is in fact the mantle cavity of the slug.
The image shows five different views of one shell of the sea snail species Chicoreus ramosus. This snail is a tropical species that is quite large and predatory.
The shell has a long siphonal canal and shows three varices per whorl. The varices are places where the shell temporarily stopped growing in overall length, and grew in thickness instead, creating in this case elaborate outgrowths as well as a red area on the outer surface of the columella. The shell of this species is in demand as a decorative object, and thus is part of the international shell trade.
The image shows five different views of one shell of the sea snail species Melo aethiopica, one of the bailer shells. This snail is a tropical species that is very large and predatory.
The shell is almost spherical in overall shape with a very large aperture and a low spire. The shell of this species is in demand as a decorative object, and thus is part of the international shell trade.
Like other species within the genus Lambis, the shell of this species has an extended siphonal canal and finger-like processes that protrude from the edge of the shell aperture, which is a bright orange in color. The shell of this species is in demand as a decorative object, and thus is part of the international shell trade.
As Euhadra peliomphala matures sexually, it develops a "head-wart" between the optic tentacles. The development of the "head-wart" parallels the development of the snail's reproductive system. The "head-wart" releases the steroid hormone, testosterone, throughout the body before mating.
The nudibranch Tambja gabrielae, from the family Polyceridae, has bright yellow spots and stripes on a dark green background. At the head end, towards the left, the two rhinophores are clearly visible, and halfway down the back of the animal its gill rosette can be seen. In this image, all of these structures are being bent back by a strong water current.
There are thousands of images available, and almost all of them are quite attractive, so please also add an encyclopedic description of the image (not of the species). Useful tips for writing decriptions can be found here: Wikipedia:Picture of the day/Guidelines. Preferred images are: featured images, interesting images, images from Africa, Asia, South America, Oceania (in order to reduce systemic bias).