ANDAMAN SEA SHELLS (SHELLS SECTION)

Samudrika Shells

1. Turbo Shell

Turbo is a genus of large sea snails with gills and an operculum, marine gastropod molluscs in the family Turbinidae, the turban snails. Turbo is the type genus of the family.

The shells are more or less highly conspiral, thick, about 20–200 mm, first whorls bicarinate, last whorl large often with strong spiral sculpture, knobs or spines, base convex, with or without umbilicus. Species in this genus have a round aperture and a solid, dome-shaped calcareous operculum. This circular operculum commences as a multispiral disc, like that of a Trochus, upon the outer side of which is deposited a thin calcareous layer by a lobe of the foot which projects partly over it. This arrangement produces an operculum which exhibits all the whorls beneath, but which is only feebly, or not obviously spiral above, from the more or less general distribution of the calcareous matter. The first Turbo species were found in the Upper Cretaceous, approximately 100 million years ago.


2. Trochus Shell

Trochus is a genus of medium-sized to large, top-shaped sea snails with an operculum and a pearly inside to their shells, marine gastropod molluscs in the family Trochidae, the top snails.

The name Trochus, according to P. Fischer was used for the first time by Guillaume Rondelet, in 1558, who assembled under this title a rather miscellaneous assortment of univalves. Linnaeus' genus Trochus is composed principally of true Trochidae, but it is now viewed as having contained species of several other very different families. Sea snails in the genus Trochus have large, thick, solid shells that have a broadly conical spire and a flat base. The periphery is angulated. The base of the shell is flat or convex. The outer and basal lips are smooth within. The columella has a strong fold above, ending in an obtuse tooth below. The interior of the shell is pearly and iridescent because of a thick layer of nacre (mother of pearl).

3. Nautilus Shell

Nautiluses are the sole living cephalopods whose bony body structure is externalized as a shell.

The nautilus shell is composed of two layers: a matte white outer layer, and a striking white iridescent inner layer. The innermost portion of the shell is a pearlescent blue-gray. The osmeña pearl, contrarily to its name, is not a pearl, but a jewellery product derived from this part of the shell. Internally, the shell divides into camerae (chambers), the chambered section being called the phragmocone. The divisions are defined by septa, each of which is pierced in the middle by a duct, the siphuncle. As the nautilus matures it creates new, larger camerae, and moves its growing body into the larger space, sealing the vacated chamber with a new septum. The camerae increase in number from around four at the moment of hatching to thirty or more in adults.  The nautilus shell presents one of the finest natural examples of a logarithmic spiral, although it is not a golden spiral. The use of nautilus shells in art and literature is covered at nautilus shell. 

4. Conus Shell

This genus shows a large variety of colors and patterns, and local varieties and color forms of the same species often occur.

The shells of Conus species vary in size. The shells are shaped more or less like the geometric shape known as a cone, as one might expect from the popular and scientific name. The shell is many-whorled and in the form of an inverted cone, the anterior end being the narrow end. The protruding parts of the top of the whorls that form the spire are more or less in the shape of another, much more flattened, cone. The aperture is elongated and narrow. The horny operculum is very small. The outer lip is simple, thin, and sharp, is without a callus, and has a notched tip at the upper part. The columella is straight. The larger species of cone snails can grow up to 23 cm (9.1 in) in length.

5. Seaurchins

Sea Urchins are a source of food for many inhabitants of the sea. The shell of the urchin (after the animal and spines have been removed) displays a beautiful symmetrical design. There are over 800 types of sea urchins found today.

Found in tidal pools and on rocks or sand in shallow waters, sea urchins are covered with long spines that they use for movement and defense. The shell of a sea urchin is called a test. It is comprised of plates that surround the urchin's soft parts. It is usually split into five main areas. Bits of seaweed that stick into the spines help provide camouflage from would-be predators. Like the starfish, the Sea Urchin's mouth is on its underside in the center. The jaw portion is sometimes referred to as Aristotle's lantern because it resembles a type of old oil lamp.

6. QUEEN SHELLS

The mature shell is typically 15–31 centimetres (5.9–12.2 in) in length, while the maximum reported size is 35.2 centimetres (13.9 in)

The shell is very solid and heavy, with 9 to 11 whorls and a widely flaring and thickened outer lip. Although this notch is not as well developed as elsewhere in the family, the shell feature is nonetheless visible in an adult dextral (normal right-handed) specimen, as a secondary anterior indentation in the lip, to the right of the siphonal canal (viewed ventrally). The animal's left eyestalk protrudes through this notch.The shells of juvenile queen conches are strikingly different in appearance from those of the adults. Noticeable is the complete absence of a flared outer lip; juvenile shells have a simple sharp lip, which gives the shell a conical or biconic outline.


7. CLAM SEASHELLS

A clamshell is a one-piece container consisting of two halves joined by a hinge area which allows the structure to come together to close. Clamshells are often made of a shaped plastic material, in a way that is similar to a blister pack.

The name of the clamshell is taken from the shell of a clam, which it resembles both in form and function. Clam shells consist of a wide variety of bi-valve shells in many shapes and sizes. Some are edible and some produce pearls. Most live in shallow waters, and the species can be found in either fresh or salt water. This popular shell has been a favorite for serious collectors and novice collectors for generations.


8.0HORN SHELLS

Spirula spirula is a species of deep-water squid-like cephalopod mollusk.

It is the only extant member of the genus Spirula, the family Spirulidae, and the order Spirulida. Because of the shape of its internal shell, it is commonly known as the ram's horn squid or the little post horn squid. Because the live animal has a light-emitting organ, it is also sometimes known as the tail-light squid. Live specimens of this cephalopod are very rarely seen, because it is a deep-ocean dweller. The small internal shell of the species is however quite a familiar object to many beachcombers. The shell of Spirula is extremely light in weight, very buoyant, and surprisingly durable; it very commonly floats ashore onto tropical beaches (and sometimes even temperate beaches) all over the world. This seashell is known to shell collectors as the ram's horn shell or simply as Spirula.


9. TRITON SEASHELLS

The larger Tritons have been used as trumpets since ancient times. For thousands of years, statues and pictures have shown the mythological god Triton or Neptune blowing the Triton shell trumpets.

This family includes some of the largest living gastropods. Most Tritons have a hairy outer covering (periostracum) that protects the shell. Tritons feed on other mollusks and starfish. They secrete a paralyzing fluid that renders their prey helpless, then they insert their mouthpart into the shell and eat the soft parts of the animal within. They dwell in tropical and warm waters and feature a thick and solid shell. Their egg capsules attach to rocks while their larvae may be free-swimming for up to three months. This accounts for the wide distribution of the family.


10. Mother of Pearls

Nacre is also known as mother of pearl, is an organic-inorganic composite material produced by some molluscs as an inner shell layer; it is also what makes up the outer coating of pearls. It is strong, resilient, and iridescent.

Nacre is found in some of the more ancient lineages of bivalves, gastropods, and cephalopods. However, the inner layer in the great majority of mollusc shells is porcellaneous, not nacreous, and this usually results in a non-iridescent shine, or more rarely in non-nacreous iridescence such as flame structure as is found in conch pearls. The outer layer of pearls and the inside layer of pearl oyster and freshwater pearl mussel shells are made of nacre. Other mollusc families that have a nacreous inner shell layer include marine gastropods such as the Haliotidae, the Trochidae and the Turbinidae.


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