(Fig. 50E, Pl. 10E)
Chionoecetes tanneri Rathbun, 1894: 76, pl. 4, figs. 1–4 (part); 1904: 174; 1925: 243, pls. 88, 89, 234. — Holmes 1900: 40. — Weymouth 1910: 35, pl. 7, fig. 19. — Schmitt 1921: 210, text fig. 131. — Garth 1958: 156, pl. I, fig. 8; pl. 16, fig. 2. — Hart 1982: 196, fig. 79. — Hendrickx 1999: 49, pl. 1A, C.
Diagnosis. Rostrum short, wide space between horns, horns slightly upturned, hooked setae present in newlysettled juvenile only. Carapace broad, swollen at branchial regions, spinous; space between branchial regions deep. Outer spine of branchial row as large as outer spine of transverse row, directly in front of it, another row of spines forming lateral supramarginal border of branchial region; spines continuing of pterygostomian region, branchial region; irregular row of small spines crossing gastric region. Orbits, outer margin of postorbital teeth, inferolateral, posterior margins of carapace armed with spinules. All spinules may be blunt in very large crabs. Male cheliped much longer than that of mature female, palm swollen, fingers long, curved. Pereopods 2–5 flattened, armed with spines, dactyls long, flat. Male carapace length 31 mm, width 29 mm; female 31 mm, width 29.1 mm.
Color in life. Bright scarlet, apices of appendages yellow. The color notes are from a crab trapped off San Clemente I., California.
Habitat and depth. Green mud, fine gray sand, 54–1960 m but usually between 200–500 m on continental slopes; may migrate vertically along bottom during year.
Range. Bering Sea to off Coronado Is., Baja California. Type locality Gulf of Farallones, California.
Remarks. The Tanner crab is edible and is the object of a fishery off Oregon. Species of Chionoecetes have a relatively thin and flexible exoskeleton in relation to their musculature, which allows easier extraction of their meat than in other spider crabs.