Prosobranchs

Class Gastropoda

Snails, sea slugs, bivalves, octopus, chitons. Second only to arthropods in numbers of species, molluscs have shown enormous evolutionary flexibility in their basic body plan of a head, a broad creeping foot, and a visceral mass containing their gut & internal organs. ~100,000 living species.

Shelled gastropods (formerly Subcl. Prosobranchia)

Subclass Patellogastropoda (true limpets)

Acmaea mitra Rathke, 1833
Phylum Mollusca, Class Gastropoda, Subcl. Patellogastropoda, Superfamily Lottioidea, Family Acmaeidae

Dunce cap limpet. Shell 35 mm high, white but usually covered with crustose coralline algae. Apex tall & centrally placed.

Common but inconspicuous, often concealed under mats of geniculate coralline algae. Feeds on crustose corallines

Geogr. Range: Aleutian Islands to Baja
Synonyms:
Similar species: other patelloid limpets in the Monterey region occur in the rocky intertidal.

Subclass Vetigastropoda ("Archeogastropoda")

Diodora aspera (Rathke, 1833)
Phylum Mollusca, Class Gastropoda, Subcl. Vetigastropoda, Superfamily Fissurelloidea, Family Fissurellidae

Keyhole limpet. Shell a tapered oval to 70 mm, triangular in profile; aperture at apex round, displaced slightly toward anterior. Radial ribs with weaker concentric sculpturing.

Common on rocks in subtidal & low intertidal. Feeds on encrusting invertebrates (sponges, bryozoans, ascidians) & algae. Reacts to predatory sea stars by fleeing & expanding mantle to cover shell (individual in photo is initiating such a response). Sometimes has a commensal polychaete Arctonoe in mantle cavity.

Geogr. Range: Aleutian Islands to Baja
Synonyms:
Similar species: Fissurella volcano occurs in the intertidal & its apex aperture is oval rather than round.

Megathura crenulata (G.B. Sowerby I, 1825)
Phylum Mollusca, Class Gastropoda, Subcl. Vetigastropoda, Superfamily Fissurelloidea, Family Fissurellidae

Giant keyhole limpet. Shell permanently covered by mantle; total length to 250 mm; soft parts usually solid black but may also be mottled. Bottom of foot yellowish-brown.

Common on rocks in kelp forests. Feeds on compound ascidians and other encrusting invertebrates.

Geogr. Range: Monterey Bay to Baja
Synonyms:
Similar species: no other limpet is as large as Megathura nor all black.

Haliotis rufescens Swainson, 1822
Phylum Mollusca, Class Gastropoda, Subcl. Vetigastropoda, Superfamily Haliotoidea, Family Haliotidae

Red abalone. Shell to 30 cm, 3-4 open holes, oval with edges slightly raised; shell red with irregular lumpy spiral ridges overlaid with fine axial striations; shell often overgrown with fouling organisms in larger individuals. Epipodium smoothly scalloped, black or banded black & cream; epipodial & cephalic tentacles black. Pictured individual may be a rare rufescens - walallensis hybrid, since it has foot & mantle of H. rufescens but shell more reminiscent of H. walallensis.

Moderately common, but patchy, in crevices where sea otters cannot reach them. Herbivorous.

Geogr. Range: Sunset Bay Oregon to northern Baja
Synonyms:
Similar species: see table

Image pictured individual is displaying its expanded-mantle flight response from a sea star.

Haliotis walallensis Stearns, 1899
Phylum Mollusca, Class Gastropoda, Subcl. Vetigastropoda, Superfamily Haliotoidea, Family Haliotidae

Flat abalone. Shell flat, narrow relative to length, 15 cm, brick red with white & bluish mottling, numerous spiral beaded ribs crossed by weaker axial striations; 4-8 oval holes with raised margins, epipodium lace-like yellow-green mottled with slender yellow green tentacles (photo is a juvenile).

Uncommon in Monterey, under rocks & in crevices. Herbivorous broadcast spawners.

Geogr. Range: British Columbia to San Diego
Synonyms:
Similar species: see table

Image Garnotia adunca on shell

Tegula brunnea (Philippi, 1848)
Phylum Mollusca, Class Gastropoda, Subcl. Vetigastropoda, Superfamily Trochoidea, Family Tegulidae

Brown turban snail. Conical rounded shell to 30 mm, light brown but usually encrusted with non-coralline red algae. Umbilicus closed (arrow); low spiral ridge on base ends in a notch & tooth on inner edge of aperture (inset). Foot black with orange margins.

Very abundant in kelp forest depths, on rocks, low-lying algae & especially on giant kelp. Herbivorous.

Geogr. Range: Cape Arago Oregon to Channel Islands
Synonyms: Chlorostoma brunneum
Similar species: Tegula montereyi & Tegula pulligo are much less round, with more straight-sided shells; both also lack orange margin on solid black foot.

Image Dodecaceria concharum (across bottom)

Tegula montereyi (Kiener, 1850)
Phylum Mollusca, Class Gastropoda, Subcl. Vetigastropoda, Superfamily Trochoidea, Family Tegulidae

Conical shell to 35 mm, sides flat with fine spiral ribs; sharply angular basal edge; inner edge of open umbilicus spirals up toward apex (arrow); low spiral ridge on base ends in notch & tooth on inner side of aperture (inset). Side of foot black with faint pale mottling.

Abundant, on rock, low-lying algae, & giant kelp. Herbivorous.

Geogr. Range: Marin County to Channel Islands
Synonyms: Chlorostoma montereyi
Similar species: Tegula brunnea is rounder with a heavier shell that lacks open umbilicus; Tegula pulligo has neither fine spiral striations on shell nor tooth + notch on columella; its open umbilicus is very different.

Tegula pulligo (Gmelin, 1791)
Phylum Mollusca, Class Gastropoda, Subcl. Vetigastropoda, Superfamily Trochoidea, Family Tegulidae

Conical smooth shell to 30 mm; whorls & base more rounded than Tegula montereyi but not as rounded as Tegula brunnea. Inner edge of aperture a flange that separates it from open umbilicus (arrow); base of shell & inner lip of aperture smooth, lacking ridge, notch or tooth (inset). Side of foot black with faint pale lines & pale margin.

Very abundant, on rocks, low-lying algae, & giant kelp. Herbivorous.

Geogr. Range: Sitka Alaska to Baja
Synonyms: Promartynia pulligo
Similar species: Tegula brunnea is more round, lacks open umbilicus; Tegula montereyi has fine spiral striations on shell & edge of open umbilicus spirals upward toward apex.

Image Garnotia adunca (on shell).

Calliostoma ligatum (Gould, 1849)
Phylum Mollusca, Class Gastropoda, Subcl. Vetigastropoda, Superfamily Trochoidea, Family Calliostomatidae

Conical, rounded, smooth shell to 25 mm, dark brown with narrow tan or dark blue spiral lines. Head & foot black. Coats shell with thin layer of slick mucus using posterior end of foot.

Very abundant, on rocks, red algae, and giant kelp. Omnivorous, but mostly browses on sponges, bryozoans, compound ascidians, hydroids & other sessile invertebrates.

Geogr. Range: Alaska to San Diego
Synonyms:
Similar species: Calliostoma gloriosum is rarer, larger & more uniformly brown with dark patches arranged in spiral bands. Other Calliostoma differ in color, size or both from C. ligatum.

Image Petaloconchus (bottom), Corynactis (left & top)

Calliostoma annulatum (Lightfoot,1786)
Phylum Mollusca, Class Gastropoda, Subcl. Vetigastropoda, Superfamily Trochoidea, Family Calliostomatidae

Conical, flat sided shell to 30 mm with beaded spiral sculpturing; shiny purple & gold. Head & foot orange with dark mottling. Coats shell with thin layer of slick mucus.

Abundant & conspicuous, on rocks, algae, giant kelp. Omnivorous, but prefers hydroids, bryozoans, sponges, compound ascidians & other colonial invertebrates.

Geogr. Range: Alaska to Baja
Synonyms:
Similar species: no other trochid species is as brightly colored as C. annulatum.

Image Diplosoma (right), Crisia (far left middle)

Calliostoma canaliculatum (Lightfoot, 1786)
Phylum Mollusca, Class Gastropoda, Subcl. Vetigastropoda, Superfamily Trochoidea, Family Calliostomatidae

Conical, flat-sided shell to 35 mm with angular basal edge and fine spiral ribbing. White with alternating thin dark brown lines. Head and foot yellowish cream with dark speckles. Shell covered with thin layer of slippery mucus.

Moderately common, especially up in the canopy of giant kelp plants. Omnivorous, but browses mainly on hydroids, bryozoans. Secretes a noxious fluorescent yellow mucus from mantle cavity as a defense against predatory sea stars.

Geogr. Range: Sitka Alaska to Baja
Synonyms:
Similar species: shape & color of shell is distinctive among local trochids.

Calliostoma gloriosum Dall, 1871
Phylum Mollusca, Class Gastropoda, Subcl. Vetigastropoda, Superfamily Trochoidea, Family Calliostomatidae

Conical, rounded shell to 35 mm with smooth whorls; dark orange-brown with dark blotches arranged in spiral rows; fine dark brown spiral markings. Head and foot light brown or tan with dark mottling. Shell often coated with thick layer of mucus.

Uncommon. More frequently encountered in deeper sites with greater water motion (e.g. Carmel Bay). Omnivorous but prefers sponges.

Geogr. Range: San Francisco to San Diego
Synonyms:
Similar species: Calliostoma ligatum is more abundant, smaller and is more distinctly banded in color.

Calliostoma tricolor Gabb, 1865
Phylum Mollusca, Class Gastropoda, Subcl. Vetigastropoda, Superfamily Trochoidea, Family Calliostomatidae

Conical, flat-sided shell to 25 mm with fine beading; shell yellow-brown to olive with several contrasting rings of alternating dark brown/purplish bars and white bars.

More typical of southern California; rare in central California. Little is known of its biology.

Geogr. Range: San Francisco to Isla San Martin, Baja.
Synonyms:
Similar species: Calliostoma ligatum is more abundant, and though it sometimes has blue rings, its shell lacks minute beading & its blue rings lack alternating white bars.

Pomaulax gibberosa (Dillwyn, 1817)
Phylum Mollusca, Class Gastropoda, Subcl. Vetigastropoda, Superfamily Trochoidea, Family Turbinidae

Large heavy conical shell 25-60 mm with beaded diagonal folds across whorls. Base flat with spiral beaded cords. Shell reddish brown, but often encrusted with algae & invertebrates. Operculum shiny white, porcelain-like. Head & foot cream-colored with fine reticulating dark lines.

Abundant but often inconspicuous due to shell fouling. On rocks with algae & invertebrates. Probably a crustose coralline grazer.

Geogr. Range: British Columbia to Baja
Synonyms: Astraea gibberosa, Lithopoma gibberosum
Similar species: Megastraea undosa is similar in shape, but much larger; it occurs in southern California southward.

Image: bryozoan Reginella hippocrepis (on shell)

Subclass Caenogastropoda ("Mesogastropoda")

Neverita lewisii (Gould, 1847)
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superorder Sorbeoconcha, Order Littorinimorpha, Family Naticidae

Moon snail. Globular light brown shell to 130 mm (usually less). Foot much larger than shell & used to burrow shallowly in fine sand.

Moderately common, partially buried in sand. Makes distinctive collar-shaped egg cases embedded with sand grains (inset). Feeds mostly on burrowing bivalves.

Geogr. Range: British Columbia to Baja
Synonyms: Polinices lewisii, Euspira lewisii
Similar species:

Neobernaya spadicea (Swainson, 1823)
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superorder Sorbeoconcha, Order Littorinimorpha, Family Cypraeidae

Chestnut cowry. Glassy brown shell to 70 mm with elongate aperture edged with rounded tooth-like denticles; shell shiny brown with whitish margins. Mantle orange-brown with dark markings, usually expanded to cover most of shell.

Moderately common but spotty; in Monterey encountered more frequently in deeper, wave-exposed sites. Feeds on sponges, also ascidians & even anemones.

Geogr. Range: Monterey Bay to Baja
Synonyms: Cypraea spadicea
Similar species: no other cowries occur in kelp forest depths in Monterey.

Pseudopusula californiana (Gray, 1827)
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superorder Sorbeoconcha, Order Littorinimorpha, Family Triviidae

Coffee bean cowry. False cowry, shell 10 mm with slit-like mid-ventral aperture; shell purple-brown with strong spiral ribs. Mantle often covers much of shell & resembles the compound ascidians on which it feeds (see photo).

Moderately common but very inconspicuous due to small size. Preys on compound tunicates.

Geogr. Range: northern California to Baja
Synonyms: Trivia californica
Similar species: Pusula (Trivia) solandri (southern Calif. only) is larger (20 mm) & its shell ribs do not cross the midline while in P. californiana they do.

Image head of Orthonopias (cntr bottom); compound tunicate next to snail is probably Ritterella

Petaloconchus montereyensis Dall, 1919
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superorder Sorbeoconcha, Order Littorinimorpha, Family Vermetidae

Tube snails. Shell attached to rock and uncoils with growth to form a tube; aperture 2 mm with tiny operculum.

Abundant but patchy; forms obvious aggregations particularly on vertical rock faces; may also occur as solitary individuals. Aggregations from gregarious larval settlement, not asexual division. Suspension feeds using mucus net.

Geogr. Range: Monterey Bay to Baja
Synonyms:
Similar species: Thylacodes squamigerus is larger (aperture 12 mm) & usually solitary in kelp forest habitats. At first glance may appear to be tube dwelling polychaetes, but closer examination shows they are not.

Thylacodes squamigerus (Carpenter 1857)
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superorder Sorbeoconcha, Order Littorinimorpha, Family Vermetidae

Shell attached to rock & uncoils with growth, forming a tube with scaly axial ridges; aperture 12 mm; lacks operculum.

Common on rocks. Solitary or in small clusters subtidally; intertidally in dense aggregations from mid-zone to lower. Aggregations arise from gregarious larval settlement, not asexual division. Suspension feeds using mucus net.

Geogr. Range: Monterey Bay to Baja
Synonyms: Aletes squamigerus, Serpulorbis squamigerus
Similar species: Petaloconchus montereyensis is smaller (aperture 2 mm with operculum) & forms dense aggregations on rock faces. Calcareous tubes of serpulid polychaetes lack sculpture & their interior is dull white rather than shiny white.

Image encrusting sponge (upper left), Astrangia (right side)

Garnotia adunca (G.B. Sowerby I, 1825)
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superorder Sorbeoconcha, Order Littorinimorpha, Family Calyptraeidae

Slipper limpet. Shell to 15 mm with distinct hooked apex that overhangs posterior end of shell; shell dark purplish brown.

Very abundant on gastropod shells. Suspension feeds using enlarged gill; protandric hermaphrodite (larger individuals are female); broods eggs in mantle cavity to crawl-out stage. Small individuals change hosts often, but become sedentary as they grow & conform to shape of host shell.

Geogr. Range: British Columbia to Baja
Synonyms: Crepidula adunca
Similar species: several other small limpets live on shells of living snails.

Image the slipper limpet is riding on Tegula pulligo.

Subclass Caenogastropoda ("Neogastropoda")

Ceratostoma foliatum (Gmelin, 1791)
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superrder Sorbeoconcha, Order Neogastropoda, Family Muricidae

Leafy hornmouth or winged murex. Shell to 100 mm with 3 wing-like axial varices & strong spiral ribbing; shell white to brown, often eroded; outer lip of aperture with large tooth (arrow); tubular siphonal canal; foot white.

Moderately common, on rock faces. Uses radula & shell tooth to bore into shelled prey, especially barnacles (Balanus spp.) but also bivalves such as Pododesmus. Lays kernal-shaped yellowish-white egg cases; may aggregate to mate.

Geogr. Range: Sitka Alaska to Baja
Synonyms: Purpura foliata
Similar species: Pteropurpura macroptera is smaller with less distinct spiral ribs & shorter varices; also lacks tooth on margin of aperture.

Pteropurpura macroptera (Deshayes, 1839)
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superrder Sorbeoconcha, Order Neogastropoda, Family Muricidae

Three-winged murex. Shell to 70 mm with 3 wing-like axial varices, often with fluted margins; shell white to brown with weak spiral ribs, often obscured by thin encrustations; lip of aperture smooth & lacks a large tooth; tubular siphonal canal; foot white.

On rocky substrate with sessile inverts. Feeds on Thylacodes, barnacles, & other sessile inverts. More common in southern California, but occasionally found in mating aggregations in Monterey.

Geogr. Range: Monterey to northern Baja
Synonyms: Murex carpenteri
Similar species: Ceratostoma foliatum is larger with wider varices, strong spiral ribs & a large tooth on the outer lip of the aperture; Pteropurpura trialata is similar but slightly larger & occurs in southern California to central Baja.

Kelletia kelletii (Forbes, 1852)
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superrder Sorbeoconcha, Order Neogastropoda, Family Buccinidae

Shell to 170 mm with wavy rounded axial ribs & fine spiral markings; obvious siphonal canal; shell white but often overgrown; foot and head yellow with white speckles and dark brown lines.

Moderately common on rocks and burrowed in sand. Snails aggregate for mating and egg laying in late spring/summer. Predators and scavengers.

Geogr. Range: Monterey to Baja
Synonyms:
Similar species: the largest predatory gastropod in Monterey kelp forests.

Hima mendica (Gould, 1849)
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superrder Sorbeoconcha, Order Neogastropoda, Family Nassariidae

Narrow spired shell to 18 mm with distinct furrow at base; short siphonal canal but long tubular siphon; fine spiral ribs with closely-spaced obvious axial ribs, color non-descript. Hydroid Stylactis often covers shell along with sand & detritus.

Abundant, on rocks, but more often in sand, shell rubble, or mud; in kelp forests, most frequent in shell rubble around bases of rocky outcrops. Scavengers & micropredators.

Geogr. Range: Alaska to Baja
Synonyms: Nassarius mendicus
Similar species: Caesia fossatus is larger and occurs in more protected sites; many other small high-spired gastropods occur in Monterey kelp forests.

Caesia fossatus (Gould, 1850)
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superrder Sorbeoconcha, Order Neogastropoda, Family Nassariidae

Broad, spired shell to 47 mm, with distinct furrow at base (covered by base of siphon in photograph); posterior end of large foot with pair of small tentacles. Shell brown with fine spiral ribs and indistinct widely-spaced axial ribs. Female in photograph is laying egg cases.

Common in protected habitats in fine sand or mud (e.g. around Monterey Wharf). Scavengers.

Geogr. Range: British Columbia to Baja
Synonyms: Nassarius fossatus
Similar species: Hima mendica is smaller & narrower and tends to occur more often in kelp forests (shell rubble around rock outcrops).

Callianax biplicata (G.B. Sowerby I, 1825)
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superrder Sorbeoconcha, Order Neogastropoda, Family Olividae

Olive snail; distinctive glossy shell to 30 mm with elongate aperture; no siphonal canal, but long siphon. When active, anterior folds of foot cover front of shell and act as a plow for burrowing.

Very abundant, burrowing in clean sand, both intertidally and subtidally. Predators & scavengers on small burrowing invertebrates.

Geogr. Range: British Columbia to Baja
Synonyms: Olivella biplicata
Similar species:

Mitra idae Melville, 1893
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superrder Sorbeoconcha, Order Neogastropoda, Family Mitridae

Elongate smooth shell to 50 mm with flat-sided whorls & long aperture; short siphonal canal; rich black periostracum & bright white foot & head.

Common, on rocks at kelp forest depths. Specialist predator on sipunculids (peanut worms), using extensible proboscis.

Geogr. Range: northern California to Baja
Synonyms:
Similar species: elongate black shell & white foot are distinctive in the Monterey region.

Image Pyura siphon (top center)

Californiconus californicus Reeve, 1844
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superrder Sorbeoconcha, Order Neogastropoda, Family Conidae

Shell obconic (inversely conical), 35 mm, brown with fine spiral and axial markings; foot & head speckled.

Common, on rocks and sand, especially among tubes of Diopatra ornata. Aggregate in late spring & summer in Monterey to mate and lay eggs on low-lying red algae (e.g. Rhodymenia). Feeds on polychaetes, molluscs, crustaceans by injecting toxin through hollow radula tooth modified as a harpoon.

Geogr. Range: Farallon Islands to Baja
Synonyms: Conus californicus
Similar species: C. californicus is the only temperate cone snail (genus is large (>500 species) but mostly tropical).

Megasurcula carpenteriana (Gabb, 1865)
Phylum Mollusca, Class Gastropoda, Subcl. Caenogastropoda, Superrder Sorbeoconcha, Order Neogastropoda, Family Pseudomelatomidae

Shell fusiform (high-spired) to 90 mm, yellowish tan with narrow dark spiral bands & fine spiral sculpturing; body pale yellow with white speckles.

Uncommon in diving depths, more abundant in deeper water; on sandy substrate. Predatory, but little else is known of its natural history.

Geogr. Range: Bodega Bay to Cedros Is., Baja
Synonyms:

Similar species: Cancellaria cooperi has similar shape & coloration, but shell is shorter & stouter with knob-like axial scupture, especially at shoulders.