Click on photo to enlarge. Scale line in photo equals 1cm unless otherwise specified.
* Species which are commonly encountered on the beach.
Boreochiton beringensis (Yakovleva, 1952)
Northern Red Chiton
very low intertidal to at least 30ml size to 35mm
northern BC to Bering Sea
This species may have red, green or blue patches on its plates.
(previous name - Tonicella beringensis)
Cryptochiton stelleri (Middendorff, 1847)
Giant Pacific Chiton or Gumboot Chiton *
intertidal to 20m size to 35cm
southern California to northern Alaska; Japan
This is a fairly common intertidal species and is the largest chiton species in the world. The girdle completely covers the plates.
The disarticulated plates are often called "butterfly shells".
(previous name - Amicula stelleri)
photographed intertidallyKatherina tunicata (Wood, 1815)Black Katy Chiton *intertidal to 40m southern California to northern Alaska; Siberia size to 15cm This is a common intertidal species with a distinct black, leathery appearance. The girdle covers everything but the very center of the plates. It can not be confused with any other species.
photographed subtidallyMopalia egretta Berry, 1919Egret-Plumed Mopaliasubtidal from 25 to 77m Washington to Alaska size to 2.5cmThis is a somewhat rare species. It can be buff colored to brown to red. The bristles are very fine and branched.
photographed subtidallyMopalia ferreirai Clark, 1991very low intertidal to 18m size to 5cmnorthern California to southern AlaskaThis
species is found in outer coastal habitat and is predominantly
subtidal. In its northern range it can occasionally be found on a
very good low tide. The plates may be variably colored and
patterned. The short bristles (about 2mm) have no groove and are
branched with 5 rows of irregular spicules. The spicules can also be
preserved specimen photographed subtidallyPlaciphorella rufa Berry, 1917Red Veiled-Chitonintertidal to 45m size to 5cmsouthern Oregon to northern AlaskaThis is rarely seen intertidally. It has red plates and a white girdle making it very distinctive. It prefers habitats with moderate to heavy currents.
Placiphorella pacifica Berry, 1919Pacific Veiled-Chitondeep subtidal to 2000m size to 4cm
central California to southern Alaska
It is milky white with a pale girdle.
There is debate as to whether this species
is synonymous with Placiphorella atlantica.
This page last revised: 8-18-2020
Mopalia lignosa (Gould, 1846)
Woody Chiton *
intertidal to subtidal northern Mexico to central Alaska size to 8cm
is a very common species. It is highly variable in color and
almost always has the distinctive streaks of lines running the length
of the chiton. The plates nearly smooth. The hairs are
unbranched and usually curved.
(synonym - Mopalia elevata)
Mopalia swanii Carpenter, 1864
Swan's Mopalia *
to 19m southern California to
northern Alaska size to 10cm
is a fairly common species. It is highly variable in color.
Sometimes individual plates may be solid in color. The
plates are wide and only moderately sculptured. The girdle is also wide and fleshy and seems almost hairless. Close inspection shows sparse, short, fine hairs which are branched with two rows of bristles on opposite sides of each hair.
photographed subtidallyTonicella insignis (Reeve, 1847)White-Line Chitonintertidal to 50m size to 6cm
northern Oregon to northern Alaska This
species is rarely found intertidally. It is reddish-brown with
lighter-toned wavy lines across the width of the plates. The
girdle is light brown.
photographed subtidally rare blue color, photo - intertidal preserved specimens
Tonicella lineata (Wood, 1815)
Lined Chiton *
intertidal to 90m southern California to northern Alaska, Japan & Siberia size to 5cm
is a very common intertidal species. The background color is
orangish but can range from pink-orange to brown-orange. Wavy
bluish-white lines run across the sides of the plates which are edged
in reddish-brown. The
lines along the head and tail plates may be wavy, but are not
usually zigzagged. The lines on the head and tail plates will also be
edged in reddish-brown. Some plates may be a solid color,
reddish tone but sometimes blue. The girdle is banded and also may vary in its colors. Very young specimens can be hard to distinguish from T. undocaerulea, when the pattern features are not yet well developed.
Tonicella rubra (Linnaeus, 1767)
Northern Red Chiton
intertidal to 145m size to 22mm
California to Arctic; in Atlantic - Connecticut and northern Europe to Arctic
is rarely found intertidally in the Pacific Northwest. The plates
are light tan with red to orange-red markings. The plates may
also be uniformly reddish. The girdle is covered in minute scales
which do not overlap.
(synonyms - Boreochiton ruber, Ischnochiton ruber)
Neah Bay, WA, preserved specimen
Tonicella cf. venusta Clark, 1999intertidal
to 140m size to 1.7cm
northern Mexico to southern
tiny species is rarely found intertidally. It has a light orange
or pink background with white zigzag lines. Light dash markings
along the center of the plates separate this species from the others.
The girdle appears sandy. (The ID on the photo is not confirmed but it conforms to all characteristics.)