Pteriomorphia

Order ARCOIDA

Anadera transversa - Transverse Ark

Morphology: Bivalve mollusk. Oblong shell with 12 ribs, umbones incurved and close to front end of shell. White with dark brown hairy periostracum. Size is 2-3 cm.

Distribution: Maine to Florida and Texas

Habitat: In mud below low water.

Life History: Suspension or deposit feeders, feed on plankton or detritus. Dioecious; fertilization occurs within mantle cavity and produces pelagic larvae.

Reference: USGS

Lunarca ovalis - Blood Ark

Morphology: Molluscan bivalve with beaks that point to the anterior side. They have an oval shell with an arched hinge line bearing about 7 teeth in front of the umbo and about 30 behind, with rear hinge teeth being the largest and angled backwards.

Distribution: North west Atlantic to the Gulf of Mexico, Caribbean Sea down to Venezuela. Found at Grice Beach.

Habitat: Typically found in the intertidal zone at the water’s edge in sandy areas, they do well on high-energy beaches.

Life History: They filter feed by pulling in water with their siphon and filtering the plankton with their gills.

Reference: Seashells of Georgia and the Carolinas By Blair Witherington, Dawn Witherington

Noetia ponderosa - Ponderous Ark

Morphology: This bivalve can reach 2 to 2.5 inches in length with raised ribs (numbering 27-31). It has V-shaped white markings near the hinge with a thick black periostracum that is worn off near the beaks.

Distribution: North West Atlantic to Gulf of Mexico and Caribbean, also in the Cayman Islands.

Habitat: Found in shallow water in sandy areas from sea level to 29 meters deep.

Life History: Filter feeder that burrows very shallow.

Reference: Encyclopedia of Life

Order MYTILOIDA

Brachidontes exustus - Scorched Mussel

Morphology: Thin, fan-shaped shell with divercating radial ribs that are most evident at the outer edges; ranges in color from blue-gray to yellow to dark brown exteriorly and purple-brown interiorly; 10-46 mm longDistribution: Western Atlantic coast from New Jersey to Argentina; Gulf of Mexico; Caribbean SeaHabitat: Intertidal rocks and oyster reefs. Euryhaline and eurythermal.Life History: Gonochoristic filter-feeders. Spawning tends to occur with broad temperature changes in the spring and fall.Reference: Smithsonian Marine Station at Ft. PierceGeukensia demissa - Ribbed Mussel

Morphology: Grooved or ribbed and oval in shape; narrow, blunt-pointed head attached to submerged substrata; glossy shells range in color from olive-brown to brown-black with some yellow exteriorly; white with purple tint interiorly; can reach 10 cm in length.Distribution: Western Atlantic coast from Gulf of Maine to Florida; Gulf of Mexico - introduced on US west coastHabitat: Submerged hard substrate, such as rocks, jetties, groins, oyster reefs, debris, etc. Highly euryhaline and eurythermal.

Life History: Gonochoristic filter-feeders; can live up to 15 years (the age can be determined by counting annual growth ribs on shell).

Reference and Picture: Smithsonian Marine Station at Ft. Pierce

Order PTERIOIDIA

Atrina seminuda - Half-naked Penshell

Morphology: Bivalve mollusk. 5-9 inches in length. Large fan-shaped shell with prominent, pointed apex. Radial rows of heavy tube like spines; 10-15 ribs. Muscle scar is well surrounded by the nacreous layer of the shell.

Distribution: North Carolina to Texas, to Argentina.

Habitat: Sandy or mud-sand areas, usually live in colonies. Bury apex deeply into the sand with the fan end of the shell projecting out.

Life History: Spin a heavy byssus to anchor the pointed end down into the substrate. Release gametes through broadcast spawning events.

Reference: gsmfc.org

Order OSTREOIDIA

Crassostrea virginica - Eastern Oyster

Morphology: Aggregating bivalve which attaches to hard substrates. Valves highly variable in shape, from round to oval, and two valves generally uneven. Colors range from grey to white, and shells possess irregularly-shaped concentric rings. Can grow to up to 115 mm in length.

Distribution: From Gulf of St. Lawrence to Gulf of Mexico, Yucatan Peninsula, West Indies, and Brazil.Habitat: Intertidal and subtidal coastal habitats waters of 10-28 psu.Life History: Ecosystem engineers, as they form dense aggregations (reefs) which are habitats for many fish and invertebrates. Clean local waters of microalgae through filter feeding.Reference: Smithsonian Field Station at Ft. Pierce

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