Phylum Mollusca

Class Gastropoda

Family Cerithiidae

Horns

Horns are herbivorous snails with no relation to the augers.  They are easily recognized by the distinct siphonal canal that may be long and recurved or a semi-circular extension of the aperture.  Axial varices indicate the old location of the aperture.

 

HAWAII

Bittium impendens

  • Uncommon on shallow reefs and tidepools

  • Light tan or purple with fine granulose spirals

  • Less than 3/8 inch

 

 

 

Ittibittium parcum

  • Abundant on algae on shallow reefs and tidepools

  • Light or dark brown

  • Less than 1/4 inch

 

 

 

Cerithium atromarginatum

  • Common on algal mat of shallow reefs and tidepools

  • Stout, fairly smooth with blunt varices

  • Less than 3/8 inch

 

 

 

Cerithium egenum

  • Common on algal mat of shallow reefs and tidepools

  • Turreted with nodular spirals and pointed varices

  • Less than 3/8 inch

 

 

 

Cerithium boeticum

 

 

 

Cerithium zebrum

  • Abundant on algae on shallow reefs and tidepools

  • Variable in color with strong beaded spirals

  • Less than 3/8 inch

 

 

 

 

Cerithium rostratum

Sandbar, Kaneohe Bay, Oahu, 3 feet

 

Sandbar, Kaneohe Bay, Oahu, 3 feet

 
Cerithium rostratum, Oahu

ROSTRATE HORN

Rarely encountered on algae & stones in shallow water.  Light with inflated whorls and finely beaded sculpture.  Attains 1 inch.  Hawaii & the Indo-West Pacific.

 

 

 

 

 

Cerithium columna

Columnar Horn, Oahu

COLUMNAR HORN

  • Uncommon on algae-covered rock in shallow water

  • Strong shell with spiral cords

  • Reaches 2 inches

 

 

 

 

Cerithium echinatum

Prickly Horn, Oahu

PRICKLY HORN

  • Common on hard reef at any depth

  • Solid shell with stout spines, often encrusted with coralline algae

  • Reaches 2 inches

 

 

 

 

Rhinoclavis articulata

Rhinoclavis articulata, Oahu

Okoe Bay, Hawaii, 50 feet

ARTICULATED HORN

  • Fairly common at scuba depths in sand

  • Taller and less heavily beaded than R. sinensis

  • Reaches 2 inches

  

 

 

 

Rhinoclavis sinensis

Rhinoclavis sinensis, Oahu

CHINESE HORN

  • Common in coarse sand pockets in shallow water 

  • Stout and more rugged than R. articulata

  • Reaches 2 inches

 

 

 

 

Rhinoclavis fasciata

Rhinoclavis fasciata, Oahu

PHAROAH'S HORN

  • Common in sand at scuba depths

  • White with variable tan marks

  • Reaches 3.5 inches

 

 

 

 

Cerithium placidum

Cerithium placidum, Oahu

PLACID HORN

  • Uncommon on reefs

  • Light with inflated whorls and fine granulose spirals

  • Reaches 3/4 inch

 

 

 

 

Cerithium interstriatum

Cerithium interstriatum, Oahu

  • Fairly common under rocks in shallow water

  • Tall, solid with inflated whorls and strongly beaded spirals

  • Reaches 3/4 inch

 

 

 

 

Cerithium nesioticum

Cerithium nesioticum, Oahu

ISLAND HORN

  • Abundant under rocks in shallow water

  • Stout with beaded spirals

  • Reaches 3/4 inch

 

 

 

Family Plesiotrochidae

Plesiotrochus luteus

  • Uncommon at scuba depths, usually empty

  • Less than 3/8 inch

 

 

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