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or Crawfish Crayfish

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CRAYFISH, or CRAWFISH (Fr. ecre visse, so not connected with "fish"), a fresh water crustacean of the family Astacid

The crayfish of the Old World belong to the genus Astacus, while those of North America east of the Sierra Nevada belong to the genus Cambarus, the latter differing by the absence of gills on the fifth or last pair of legs. An interesting feature in geographical distribution is the occurrence of half a dozen species of the European genus Astacus in the streams draining the Pacific Coast from British Columbia to California. East of the Rocky Mountains, from

the Great Lakes to Guatemala, there occur be tween 30 and 40 species of Cctmbarus. These extend to eastern New York west of the Hud son River, and a single species (C. bartoni) occurs under stones in certain lakes of northern Maine as also in Lake Champlain and the Great Lakes, extending southward to Kentucky and the District of Columbia.

The presence of the Eurasian Astacus on the Pacific Coast indicates their gradual migration from eastern Asia, at a time when Bering Strait was dry land. In certain characters the Amur land and Japanese Astaci differ from the Ponto caspian and the west American Astaci and approach the Cambari of eastern North Amer ica. This is also paralleled in the distribution of many plants and insects.

The family to which the crayfish belongs dates as far back as the Jurassic Period, and in Europe Astaci first appear in the Upper Creta cean. • In North America fossil Astaci (Cam barus primceves) occur in the Lower Tertiary beds of the western border of Wyoming. Cope discovered fossil Astaci in the late Pliocene beds of Idaho. Astacus probably originated in western America, since it is found fossil throughout the Tertiary.

Crayfishes are of no little economic import ance from the fact that in the course of their extensive fossorial operations they undermine dams, and it is supposed that the inundations of the Mississippi River and the breaks in the levees may be due largely to the mining habits of these animals. For the blind crayfish see CAVE-DWELLING ANIMALS. Consult Fisher, "Crayfish as Crop Destroyers)) in (Washington 1912) ; Huxley, 'The Cray fish' (London 1887) ; Hagen, "Monograph of the North American Astacide (in the 'Illus trated Catalogue of the Museum of Compara tive Zoology,' No. III, Cambridge 1870) ; "Revision of the Astacidm* (in