Phylum Mollusca

Class Bivalvia

Bivalves

Mollusks with left & right shells called valves attached by a hinge.  The muscular foot is reduced in some families.  Sessile species are typically attached to the substrate by tough byssal threads.  They feed by filtering phytoplankton & bacteria from the water column and may not be safe to consume after blooms of toxic dinoflagellates, sometimes referred to as red tides.

HAWAII

Family Arcidae

Arc Shells

 Arca ventricosa

Kewalo Pipe, Oahu, 50 feet

 

Waimea Bay, Oahu, 30 feet

 

Byssus & scar, Lahilahi Cavern, Oahu, 60 feet

Abundant on vertical faces at scuba depths.  Snaps tightly to substrate when disturbed.  Attains 3 inches.  Hawaii & the Indo-Pacific.

Barbatia (Acar) divaricata

Ala Moana, Oahu, 30 feet

 

 

Kewalo Pipe, Oahu, 50 feet

 

Common in groups under stones at any depth.  Attains 1 inch.  Hawaii & the Indo-Pacific.

Barbatia tenella

Kaupo, Oahu, 10 feet

 

Uncommon under stones at any depth.  Shells are covered with thin periostracum.  Attains 1 inch.  Hawaii & the Indo-Pacific.

Barbatia decussata

Kaneohe Bay, Oahu

Rare under dead coral in Kaneohe Bay.  Attains 3 inches.  Hawaii & the Indo-Pacific.

Barbatia nuttingi

Makapu'u, Oahu

Uncommon under stones at any depth.  Attains 1/2 inch.  Endemic to Hawaii.

Family Mytilidae

Mussels

Brachidontes crebristriatus   

Kaupo, Waimanalo, Oahu

 

Makapu'u, Oahu, 10 feet

 

 

Makai Pier, Waimanalo, Oahu

 

 

Puako, Hawaii

 

 

Diamond Head, Oahu

HAWAIIAN MUSSEL

Forms mats in rough shallow water among algal turf & sand.  Attains 1 inch.  Endemic to Hawaii.

Lithophaga fasciola

Ala Moana, Oahu, Hawaii

Common in burrows of limestone reef rock at any depth.  Preyed upon by murex shells.  Attains 1 inch.  Endemic to Hawaii.

Modiolus matris  

Kaupo, Oahu, Hawaii

Uncommon under stones in 15 to 30 feet.  Broadly rhomboidal, orange-brown to red with thin hairy periostracum.  Fine concentric growth rings.  Attains 1/2 inch.  Endemic to Hawaii.

Septifer bryanae

Mokapu, Oahu, 130 feet

Common under stones or in algal mat to 100 feet.  Slipper shaped, green, yellow, red, or brown.  Shell covered by thin hairy periostracum.  Attains 3/4 inch.  Hawaii & the Marshall Islands.

Family Pinnidae

Pen Oysters

Streptopinna saccata

Haleiwa Trench, Oahu, 60 feet

 

Kewalo Pipe, Oahu, 50 feet

Sand Island Pipe, Oahu,  70 feet

BAGGY PEN SHELL

Uncommon in sand beneath rocks and in narrow crevices.  Up to 5 inches wide.  Hawaii & the Indo-West Pacific.

Pinna muricata

Mokapu, Oahu, 260 feet

 

Ft. Kamehameha, Oahu, 3 feet

PRICKLY PEN SHELL

Rare in sand except in very deep water where they form beds.  About 6 inches.  Hawaii & the Indo-West Pacific.

Pinna bicolor

Sea Tiger, Oahu, 120 feet

BICOLOR PEN SHELL

Rare in sand except in very deep water.  About 6 inches.  Hawaii & the Indo-West Pacific.

Family Pteriidae

Pearl Oysters

Pinctada margaritifera 

Blowhole, Oahu, 30 feet

 

Lanai Lookout, Oahu, 30 feet

Sharks Cove, Oahu, 25 feet

 

 

Juvenile, Kewalo, Oahu, 80 feet

 

Kewalo Hump, Oahu, 90 feet

Pokai Bay, Oahu, 15 feet

BLACKLIPPED PEARL OYSTER

Uncommon in shallow water and scuba depths firmly attached to the substrate.  Easily identified by fringes along opening.  Produces high-quality pearls and cultured extensively in French Polynesia.  Formerly abundant and harvested to near-extinction at Pearl Harbor and Pearl & Hermes Reef.  It is illegal to collect this species.  Hawaii & the Indo-West Pacific.

Pinctada radiata

PEARL OYSTER

Uncommon in harbors and bays with freshwater input.  Margin not fringed.  Up to 4 inches.  Hawaii & the Indo-Pacific.

Pteria brunnea

Kaumalapau, Lana'i, 140 feet

 

Red Hill, Hawaii, 100 feet

Molokini Back Wall, 75 feet

WINGED PEARL OYSTER

Uncommon on Antipatharians at depths greater than 60 feet.  Up to 4 inches.  Endemic to Hawaii.

Family Isognomonidae

Toothed Pearl Oysters

Isognomon californicum   

Kapoho Point, Kailua, Oahu

 

Makai Pier, Waimanalo, Oahu

Diamond Head, Oahu

BLACK PURSE SHELL

Common on rocks in the splash zone.  About 1.5 inch.  Endemic to Hawaii.

Isognomon incisum   

Common in crevices in shallow water.  Attains 3 inches.  Endemic to Hawaii.

Isognomon perna

Kapoho Point, Kailua, Oahu

 

Ft. Kamehameha, Oahu, 3 feet

 

Wailupe, Oahu, 2 feet

BROWN PURSE SHELL

Common under rocks in shallow water.  Tan with radiating brown ribs.  About 2 inches.  Hawaii & the Indo-Pacific.

Isognomon legumen

Portlock, Oahu, 35 feet

 

Kewalo Pipe, Oahu, 50 feet

Sand Island Pipe, Oahu, 70 feet

Uncommon at scuba depths.  Shell is quite thin with fine concentric growth rings, cream with white interior.  About 2 inches.  Hawaii & the Indo-Pacific.

Family Pectinidae

Scallops

Laevichlamys irregularis

Kewalo, Oahu, 60 feet

IRREGULAR SCALLOP

Uncommon under stones and in dead coral at scuba depths.  Attains 1.5 inch.  Seychelles to Hawaii & the Tuamotus.  Formerly known as Chlamys irregularis.

Chlamys coruscans hawaiensis   

HAWAIIAN DWARF SCALLOP

Endemic Hawaiian subspecies.  Common in dead coral, under stones, or embedded in sandy algal mat.  Attains 3/4 inch.

Decatopecten noduliferum

 

 

Sea Tiger, Oahu, 120 feet

SUNRISE SCALLOP

Uncommon in sand & rubble in deep water.  Worn shells often beach collected during large winter surf.  Attains 1 inch.  Hawaii & the Indo-West Pacific.

Family Spondylidae

Thorny Oysters

Spondylus violacescens

Blowhole, Oahu, 20 feet

 

Kahe Point, Oahu, 20 feet

Sea Tiger Wreck, Oahu, 95 feet

CLIFF OYSTER

Common on vertical surfaces exposed to current or surge.  Attains 6 inches.  Inner margin is purple with brown ribs.  A Pearlfish inhabits the mantle cavity of some oysters.  Spondylus tenebrosus is a synonym.  Hawaii & the Indo-Pacific.

Spondylus nicobaricus

Sharks Cove, Oahu, 25 feet

Juvenile, Kewalo Pipe, Oahu, 50 feet

SPINY OYSTER

Common under stones and shady vertical surfaces.  Interior and lip is white.  Attains 4 inches.  Spondylus hystrix is a synonym.  Hawaii & the Indo-Pacific.

Spondylus linguaefelis   

South Shore, Oahu, 90 feet

Rare on walls & cavern ceilings in deep water.  Yellow, orange, or wine.  Attains 3 inches.  Endemic to Hawaii.  Also known as Spondylus gloriosus.

Family Anomiidae

Saddle Oyster

Anomia nobilis

Common in harbors.  Lower valve has a hole where the byssus protrudes for attachment to the substrate.  Attains 3 inches.  Hawaii & the Indo-Pacific.

Family Limidae

File Oysters

Lima lahaina   

LAHAINA FILE OYSTER

Uncommon in dead coral deeper than 80 feet.  Living animal is bright orange.  Attains 1 inch.  Endemic to Hawaii.

 Family Ostreidae

True Oysters

Crassostrea virginica

Moku O Loe, Kaneohe Bay, Oahu, 1 foot

AMERICAN OYSTER

Edible oyster introduced to Hawaii from the Atlantic & Gulf coasts of the United States.  Common on seawalls in harbors but infected by a larval tapeworm.  About 4 inches.  

Dendostrea sandvicensis   

Sea Tiger Wreck, Oahu, 80 feet

 

Moku O Loe, Kaneohe Bay, Oahu, 3 feet

HAWAIIAN OYSTER

Abundant in shallow bays and harbors.  Up to 2 inches.  Endemic to Hawaii.

Family Gryphaeidae

Parahyotissa numisma

Portlock, Oahu, 35 feet

HAWAIIAN OYSTER

Common on the underside of ledges and rocks in shallow water.  Attains 2 inches.  Hawaii & the Indo-Pacific.  Ostrea thaanumi & Ostrea hanleyana are synonyms.

Family Chamidae

Rock Oysters

Chama iostoma

 

Ft. Kamehameha, Oahu, 3 feet

JEWEL OYSTER

Locally common in shallow water and tidepools.  Shell is very thick, smooth with fine concentric growth rings.  Interior margin is purple.  Up to 5 inches.  Hawaii & the Indo-West Pacific.

Chama fibula

Sea Cave, Oahu, 80 feet

DWARF JEWEL OYSTER

Rare in the main Hawaii Islands but common in the NWHI.  Shell is very thick, smooth with fine concentric growth rings.  Interior white.  Up to 1 inch.  Hawaii & Pacific.

Family Lucinidae

Codakia punctata

Uncommon in sand & rubble in shallow water.  Attains 3 inches.  Hawaii & the Indo-Pacific.

Ctena bella

Very common in sand at any depth.  Attains 1 inch.  Hawaii & the Indo-Pacific.

Lucina edentula

Kaneohe Bay, Oahu

Uncommon in sand at scuba depths.  Shell is strongly inflated.  Attains 1 inch.  Hawaii & the Indo-Pacific.

Family Lasaeidae

Nesobornia bartschi

Makapu'u tidepool, Oahu

Groups are common under stones in shallow water.  Shell is semi-translucent.  Able to move freely using highly flexible foot.  Attains 1/2 inch.  Hawaii & the Indo-Pacific.

Kellia hawaiensis   

Found in dead coral at scuba depths.  Shell is translucent.  Attains 3/16 inch.  Endemic to Hawaii.

Family Sportellidae

Hitia ovalis   

Uncommon in sand at deeper scuba depths.  Shell is solid and opaque.  Attains 1/3 inch.  Endemic to Hawaii.

Family Carditidae

Cardita thaanumi   

Uncommon under stones at any depth.  Attains 3/4 inch.  Endemic to Hawaii.

Family Cardiidae

Fragum mundum

Fairly common in algal mat in shallow water.  Attains 3/4 inch.  Hawaii & the Indo-Pacific.

Trachycardium orbita

Sand Island Pipe, Oahu, 100 feet

 

Mokuleia, Oahu, 100 feet

Uncommon in coarse sand & rubble.  Attains 3 inches.  Hawaii & the Indo-Pacific.

Family Tellinidae

Tellina scobinata

Sand Island Pipe, Oahu, 100 feet

 

Portlock, Oahu, 35 feet

RASP TELLIN

Buried in sand at scuba depths.  Attains 2.5 inches.  Hawaii & the Indo-Pacific.  Formerly known as T. elizabethae.

Tellina crucigera

Empty shells are fairly common at scuba depths.  Attains 2 inches.  Hawaii & the Indo-Pacific.

Macoma dispar

Locally common in sand in brackish water bays.  Attains 1.5 inch.  Hawaii & the Indo-Pacific.

Tellina (Arcopagia) robusta

Uncommon in sand at scuba depths.  Attains 3/4 inch.  Hawaii & the Indo-Pacific.

Tellina (Quidnipagus) palatam

Locally common in silty sand in shallow water.  Attains 4 inches.  Hawaii & the Indo-Pacific.

Family Trapeziidae

Trapezium oblongum

Uncommon under dead coral or sandy rubble in shallow water.  Attains 2 inches.  Hawaii & the Indo-Pacific.

Family Veneridae

Lioconcha hieroglyphica

Uncommon in sand at any depth.  Live shells coated with a thick brown periostracum.  Attains 1.5 inch.  Hawaii & Micronesia.

Periglypta reticulata

Fairly common in sand under stones at any depth.  Attains 3 inches.  Hawaii & the Indo-Pacific.

Globivenus toreuma

Uncommon in sand at scuba depths.  Attains 1 inch.  Hawaii & the Indo-Pacific.  Formerly known as Venus toreuma.

Venerupis (Ruditapes)  japonica

Rare in sand in shallow water in except SE Kaneohe Bay.  Attains 2 inches.  Introduced to Hawaii & North America from the Indo-Pacific.  Formerly known as Tapes japonica.

Family Gastrochaenidae

Gastrochaena cuneiformis

Breathing tubes, Kewalo Hump, Oahu, 90 feet

Inhabits burrows in massive Porites coral.  Attains 1.5 inch.  Hawaii & the Indo-Pacific.

Family Hiatellidae

Hiatella arctica

Ala Moana, Oahu, 50 feet

Inhabits crevices or burrows in shallow water.  Attains 2 inches in cold water, but less than 1 inch in Hawaii.  Worldwide distribution.

 


INDO-PACIFIC excluding HAWAII

Family Tridacnidae

Giant Clams

Tridacna sp.

Bora Bora, Society Islands

 

TRIDACNA CLAMS

Family Pectinidae

Scallops

Pedum spondyloideum

Bora Bora, Society Islands

 

 

Common in Porites coral throughout the Indo-Pacific except Hawaii.  Two inches wide.

Family Limidae

File Oysters

Limaria fragile

Mamanucas Is., Fiji

FRAGILE FILE OYSTER

Uncommon in dark holes and under stones at scuba depths.  Mantle displays flashing blue lines.  About 1.5 inches wide.  Indo-Pacific.

 


NORTHEAST PACIFIC

Crassedoma giganteum

Ogden Point, Victoria, Canada, 25 feet

ROCK SCALLOP

Common on rocks.  Up to 8 inches.   British Columbia to Baja California.

Mytilus californianus

Ogden Point, Victoria, Canada, 5 feet

CALIFORNIA MUSSEL

Abundant in beds in shallow water exposed to waves.  Black with radiating ribs.  Up to 8 inches.

Mytilus edulis

Intertidal zone, Victoria, Canada

BLUE MUSSEL

Abundant in clusters in shallow quiet water and harbors.  Shell with fine concentric growth rings.  About 3 inches.

Chlamys hastata

Ogden Point, Victoria, Canada, 40 feet

SPINY SCALLOP

Locally common in areas exposed to current at scuba depths.  Shell has strong ribs.  Up to 3.5 inches.  Alaska to Southern California.

Chlamys rubida

Ogden Point, Victoria, Canada, 40 feet

PACIFIC PINK SCALLOP

Locally common in areas exposed to current at scuba depths.  Shell has low rounded ribs.  Up to 3 inches.  Alaska to Southern California.


 

 

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