Black-ribbed Limpet or Star Limpet
Phylum Mollusca, Class Gastropoda, Order Patellogastropoda, Family Nacellidae, Genus Cellana, Species Cellana exarata · Nacellidae (True Limpet family) · Gastropod (univalve), whole shell, cap-shaped or conical shape
Species
Cellana exarata
Shell Type
Gastropod (univalve), whole shell, cap-shaped or conical shape
Family
Nacellidae (True Limpet family)
Size
Approximately 1.5 to 2 inches in length, which is average for a mature adult specimen of this Hawaiian endemic species. Adults typically range from 1 to 2.5 inches.
Color & Pattern
Distinctive striking pattern featuring prominent, raised radial ribs that are deep black to dark brown, contrasting sharply against a whitish or pale grey background. The apex is central or slightly anterior, often worn or eroded to a pearly white. The interior is silvery, porcelain-white with a dark central horseshoe-shaped muscle scar.
Rarity
Common
Habitat
Found on high-energy, wave-swept intertidal basalt rocks and bench formations, firmly clamped down in the supratidal and mid-intertidal zones where they are exposed to heavy surf and drying sun.
Geographic Range
Endemic to the Hawaiian Islands, commonly found throughout the main and northwestern Hawaiian archipelago.
Description
A robust, low-conical limpet with a sturdy shell built to withstand powerful wave action. The exterior features strong, coarse radial ribs that create a scalloped, serrated margin along the perimeter. The apex is positioned slightly forward of the center. Its heavy, solid construction and dramatic black-and-white ribbing make it one of the most visually striking and recognizable limpets of the Hawaiian coastline.
Key Features
Coarse, prominent black radial ribs alternating with pale interspaces, a strongly scalloped margin, and an endemic Hawaiian distribution combined with a strict high-intertidal rocky habitat.
Collector Value
Moderately high for regional collectors and enthusiasts of Hawaiian shells. While common locally, good specimens with vibrant, unblemished black ribs and clean interiors are prized by shell crafters and regional specialists. Typically valued as an inexpensive to moderately priced local shell, though culturally priceless.
Condition Notes
Good to Fine condition. The shell is intact with strong structural integrity, well-defined black ribs, and minimal wear around the apex, indicating a healthy specimen collected fresh.
Interesting Facts
Cellana exarata is endemic to Hawaii and is locally known as 'opihi makaiauli. Opihi are a legendary delicacy in Hawaiian culture, traditionally harvested by free-divers along dangerous, wave-swept cliffs, earning them the nickname 'fish-eye' or the perilous label of 'suicide opihi' due to the danger involved in gathering them.
Ecological Role
Acts as an important herbivorous grazer in the intertidal ecosystem, scraping microalgae and diatom films off rocks, which helps maintain bare rock surfaces and prevents algal overgrowth. They serve as a food source for shorebirds and reef fish, and play a crucial cultural role in Hawaiian marine resource management.
Similar Species
Cellana sandwicensis (Yellow-foot opihi) and Cellana talcosa (Kolea opihi), which can be distinguished by differences in rib texture, coloration, and preferred intertidal zones.
Beach Finding Tips
Look along rocky intertidal benches, basalt outcroppings, and tide pools during extreme low tides, especially on windward shores. Finding live specimens or fresh dead shells requires caution due to dangerous rogue waves crashing against the rocks.
Notes
Goat Island near Laie Hawaii