Phylum Mollusca

 

Class Bivalvia

Subclass Pteriomorpha

Order Mytilodia

Family Mytilidae (mussels)

Mytilus californianus (California blue mussel)

This mussel has 2 adductor muscle scars, with the anterior muscle smaller and located near the beak. The shell color is brown or black, and is cylindrical or tapering anteriorly. Found in the middle intertidal zone, usually in large beds, Mytilus californianus is abundant in exposed rocky intertidal zones. The shell has irregular radial ribs, especially on the posterior end, and the anterior adductor scar is located more anteriorly than in Mytilus edulis.

 

Mytilus edulis (Bay mussel)

This mussel is similar to Mytilus californianus; however, it is smaller in size, its shell is generally smooth, and the anterior adductor muscle scar is on the anteroventral margin. It is abundant on wharf piling and rocks. Among these creatures are goose-neck barnacles.

 

Order Pterioida

Family Ostreidae

Crassostrea gigas (Japanese/Pacific oyster)

This common oyster is large (up to 30 cm), thick, with its inner margin smooth near the hinge. The shell shape varies from oval to very long and narrow; it has prominent, projecting fluting and deep radial grooves; the muscle scar is violet or whitish; the external color is gray-purple; it is either attached or free-living in the mud.

 

Family Pectinidae

Hinnites giganteus (giant rock scallop)

This scallop has a fanlike shell, with radiating ribs and with the dorsal margin produced into triangular "ears", at least in young; it is free-living when young but attaches as an adult to rocks and pilings where its growth becomes irregular.

 

Subclass Heterodonta

Class Cephalopoda

Class Gastropoda

Subclass Opisthobranchia

Order Anaspidea

Order Celphalaspidea

Order Notaspidea

Order Nudibranchia

Subclass Prosobranchia

Order Archaeogastropoda

Superfamily Patellacea (true limpets)

Family Acmaeidae

Acmaea mitra

This limpet is cap shaped, the ends of the muscle scar joined by a faint, thin, simply curved line; the shell length is not more than 60 mm. Its surface is smooth, the aperture is oval, the color is entirely white, the apex is central, and its shape is high-conic with straight slopes. Its sculpture may be concealed by pink coraline algae. It is usually found in the low intertidal zone.

 

Collisella digitalis

This limpet is cap shaped, the ends of the muscle scar are joined by a faint, thin, simply curved line; the shell length is not more than 6 cm. Its surface has heavy radial ribs; its anterior slope is generally concave, while the posterior is convex; the apex is generally above or, at times, overhanging the anterior margin; the ribs are strongest on the posterior slope, and may be absent on the anterior end. It is usually in the high intertidal zone, often on vertical rock faces.

 

Collisella limatula

This limpet is cap shaped, the ends of the muscle scar are joined by a faint, thin, simply curved line and the shell length is not more than 6 cm. It has an oval aperture, fine scaly radial ribbing, and a serrate margin. The color is buff yellow with fine darker mottlings, or green brown with white tessellations or bands; the sides of the foot and head are black to gray in contrast to a white undersurface. It is usually found in the intertidal zone.

 

Collisella pelta

This limpet is cap shaped, the ends of the muscle scar joined by a faint, thin, simply curved line; the shell length is not more than 6 cm. Its surface has heavy radial ribs; the apex is subcentral; the ribs are generally equally developed on all slopes. The color is various, brown, green, or greenish-black, and checkered with white tessellations or peripheral rays and bands of white. It is generally taller than other Collisellas. It is usually found in the intertidal zone.

 

Collisella scabra

This limpet is cap shaped, the ends of the muscle scar joined by a faint, thin, simply curved line; the shell length is not more than 6 cm. Its surface has heavy radial ribs; the rib surfaces are usually light-colored with darker spaces between; the ribs project strongly in all directions, forming a strong scalloped margin. The apex is usually about 1/3 of the distance from the anterior end; the anterior slope is convex; the animal has black spots on the head and sides of the foot. It is usually found in the high intertidal zone, often on horizontal rock surfaces.

 

Lottia gigantea (owl limpet)

This limpet is cap shaped, the ends of the muscle scar are joined by a sinuous, deep-cut line; the shell is long-oval, large (length up to 10 cm) and heavy; and the apex is near the anterior end. The color is maculated brown and white; the inner margin is dark brown, with a prominent, owl-shaped muscle scar at the center. It is usually found in the mid-intertidal zone.

 

Notoacmea persona

This limpet is cap shaped, the ends of the muscle scar joined by a faint, thin, simply curved line. Its surface is smooth; the aperture is oval; the apex is markedly directed anteriorly. The shell is large (up to 5 cm in length); the anterior slope is straight, the other slopes convex; the color is usually an olivaceous green with scattered white tessellations or rays; the apex erodes to brown with 2 lateral steaks of white dots. It is usually found in the high intertidal zone in sheltered, shaded areas.

 

Notoacmea scutum

This limpet is cap shaped, the ends of the muscle scar joined by a faint, thin, simply curved line. Its surface is smooth; the aperture is oval; the apex is subcentral. The shell is thick, large (up to 6 cm); it has a color pattern of variable spotting, with a black margin. It is usually found in the intertidal zone.


Family Fissurellidae

Diodora aspera (keyhole limpet)

This limpet is cap shaped, and has a small hole at the apex; it has radial sculpture with every 4th rib larger than the others, and has weaker concentric sculpture. The shell color is made up of gray-brown radiating bands on a grayish white background. It is usually found in the low intertidal zone under rocks and in crevices.

 

Family Haliotidae

Haliotis rufescens (red abalone)

This snail is spirally coiled, and has an aperture without an interior siphonal canal; the shell is broad, ear-shaped, and with a row of holes along one side. The holes are oval and raised above the shell surface, and the color is a dull brick red. It is found in low intertidal to sublittoral zone.

 

 

Superfamily Trochacea (turban and top snails)

Family Trochidae

Caliostoma canaliculatum

This snail is spirally coiled and has an aperture without an interior siphonal canal. The interior of shell is pearly, and the base of the columella lacks nodes. The shell is small to medium sized (up to 4 cm), with numerous spiral ribs. The whorls are flat-sided, and the color is yellowish tan to white or buff, with prominent revolving ridges paler in color than the interspaces, and there is a blue stain next to the columella. It is usually found in the low intertidal zone.

 

Tegula brunnea (brown turban)

This snail is spirally coiled, has an aperture without an anterior siphonal canal, the interior of the shell is pearly, and the base of the columella has small nodes. The columellar nodes are strong, and the shell is 5 cm or more in height. The umbilicus is covered shut by a callus. The color is brown to orange-brown, and it has 1 tooth on the columella. It is found in the middle and low intertidal zones.

 

Tegula funebralis (black turban)

This snail is spirally coiled, and similar to its cousin Tegula brunnea. However its color is purplish black to black, it has a scaly band below the suture, and 2 teeth on the columella.

 

Tegula montereyi

This snail is spirally coiled, and is very similar to Tegula brunnea; however, its umbilicus is uncovered/open. The top of the inner lip recedes into the aperture, and the umbilicus defined by a strong spiral cord.

 

Tegula pulligo

This snail is spirally coiled, is very similar to Tegula montereyi, and also has an open umbilicus. However, the top of the inner lip is produced into a flange on the apertural side of the umbilicus, and there is no strong spiral cord defining the umbilicus. Its color is brown or gray, at times with orange, white, or brown spots on periphery.

 

Order Mesogastropoda

Family Calyptraeidae

Crepidula adunca (slipper shell)

This shell is cap shaped, and it has an interior with a deck or platform on the posterior end attached on both sides of the shell. The apex overhangs the posterior margin of the shell, and is distant from the margin. The deck corners are produced, extending forward on both sides, and the color is dark brown. It is found in the intertidal zone, usually attached to snails such as Tegula.

 

Crepidula fornicata (slipper shell)

This shell is cap shaped, is larger than Crepidula adunca, and has an interior with a deck or platform on the posterior end attached on both sides of the shell. The apex is strongly turned to one side and united with the margin of the shell, the deck margin is waved, and the color is a dirty white with brown blotches or wavy chestnut-colored markings. It is usually found in the intertidal zone.


Family Littorinidae

Littorina littorea (periwinkle)

This snail is spirally coiled, has an aperture without an anterior siphonal canal, and the interior of shell is porcelianlike, not pearly. The diameter of the shell is equal to or less than the height, the columella lacks strong conspicuous folds, the shell has few whorls, and the columella is shelf-like. It is small, with a brown-gray to black shell. It is is usually found on rocks in the upper intertidal zone.

 

Littorina planaxis (periwinkle)

This snail is spirally coiled, is similar to its cousin Littorina littorea, and the two are found together; however,the periwinkle is larger and different in color. The shell is stout and robust; the columella broad, flat, and polished, with a narrow white band inside the aperture. Its color is "checkerboard" - gray-brown with white maculations.

 

Order Neogastropoda

Family Olividae

Olivella biplicata

This pretty snail is spirally coiled, has an aperture with an anterior siphonal canal, and the aperture is entire at the posterior end. The aperture is less than 3/4 the length of shell, the columella has folds at its base, and the shell is unsculptured and polished. The shell is about 3 cm in length, broad and robust, and variously colored, from almost all white to a black-grey, and often violet at the base. The fold at the base of the columella often has several incised spiral lines. It is usually found in the middle intertidal zone.

 

Family Thaididae

Acanthenia spirata

This snail is spirally coiled, and has an aperture with an anterior siphonal canal, with the aperture entire at the posterior end. The columella doesn't have any folds, the anterior canal is short, and the aperture is 1/2 the length of the shell or less. It has an outer lip with a projecting tooth near the base, its color is white with revolving interrupted brown bands, and it has a prominent keel at the shoulder. It is usually found in the middle intertidal zone.

 

Nucella canaliculata (whelk)

This snail is spirally coiled, has an aperture with an anterior siphonal canal, and the aperture is entire at the posterior end. The columella is without folds, the anterior canal is short, and the aperture is 1/2 the length of the shell or less. The outer lip is smooth or evenly toothed, the base and spire have similar sculpture, the shell has smooth, closely set spiral ridges, and an elongate, narrow umbilical chink. It is usually found in the middle intertidal zone.

 

Subclass Pulmonata

Class Polyplacophora (chiton)

Cryptochiton stelleri (giant or gumboot chiton)

This chiton is the largest of chitons, growing up to 33 cm in length. A thick, brick-red or reddish brown, leathery mantle covers the shell plates-- hence the name, 'cryptochiton.' Commonly mistaken for a giant sea cucumber, the gumboot chiton can be found next to deep pool or channels.

 

Moplaia ciliata (hairy chiton)

This is the most common chiton found at Pillar Point. It grows up to 8 cm long and is oval in shape. Its color varies, many times with combinations of green, red, brown, or yellow patches. There is a distinctive notch at the tail end and a wide thick girdle. It is densely covered with curly brown hairs. The hiary chiton is commonly found in crevices and under rocks in the middle to low intertidal zones.

 

Moplaia muscosa (mossy chiton)

This strange looking organism is commonly found on rocks in the tidepools, particularly between the lower and middle intertidal zones. They range in size up to 9 cm long. This creature is commonly dull brown, blackish olive or grayish in color and has a stiff oval shaped body with brownish-red bristles on the lower end of their girdle plates.

 

Stenoplax heathiana (green marbled chiton)

Commonly found under rocks or embedded in sand, this light to dark greenish gray colored chiton grows up to 11 cm in length and is twice as long as it is wide.

 

Tonicella lineata (lined chiton)

Usually found on rocks covered with coralline algae, this elongated oval shaped chiton measures up to 5 cm long. Its shell plates are usually light reddish and marked with zigzag lines or alternating colors of yellowish or greenish bands.