Rostrum a low median angle on the anterior margin of the carapace. Eyes elongate triangular, pointed, reaching with their full length beyond the rostrum. Antennal angles blunt, without spine. Antennal peduncle practically as long as the antennular peduncle.
Third maxilliped with merus and ischium strongly expanded forming an operculum; the last three segments of the maxilliped less than half as wide as the merus, but not very slender, twice or less than twice as long as wide. Large chela of adult male with the concave part of the anterior margin of the palm above the base of the fixed finger absent or hardly noticeable. Carpus distinctly longer than palm. Merus with a large and rather wide hook-shaped process in the basal part of the lower margin; in the females this process is reduced to a small triangular tooth.
Telson quadrangular, longer than wide and slightly narrowing posteriorly; posterolateral angles rounded. Posterior margin with a small triangular median denticle; no other spines or teeth on telson. Endopod of uropod broad, quadrangular or slightly triangular, with rounded angles and slightly longer than telson.
Type locality of C. gigas: "in freto Pugettensi, Oregoniae" ( = Puget Sound, Washington State, USA). Type in USNM, now lost.
Type locality of C. longimana: "Puget Sound" ( = Steilacoom on Puget Sound between Tacoma and Olympia, Washington State, USA). Type material in the Museum of the Boston Society of Natural History, in ANSP (not located in 1989), and in USNM (lost).
Eastern Pacific region from Vancouver Island (British Columbia, Canada) to San Quintin Bay (N.W. Baja California, Mexico).
Habitat and Biology:
Lower intertidal zone of tidal flats on the sea coast and in estuaries. Burrowing in soft substrate of sand and mud. Thespecies is less frequent than C. californiensis, which lives in the same habitat.
Total body length about 12.5 to 15 cm; a larger species than C. californiensis.
Interest to Fisheries:
Like C. californiensis and C. biffari, the present species is taken as fish bait on the California coast and sold in bait shops. The animals are caught in the same way as C. californiensis.