390 



CRUSTACEA 



yellowish uiiderneatli : Atlantic coast from Labrador to North Carolina, 

 in shallow water in summer and in deeper water in winter. Lobsters are 

 caught mostly oft' the coast of Canada and the New England states and 

 _ are our most important 



IS 



food crustacean. The an- 

 nual catch has amounted 

 to over 100,000,000 in 

 some years but is now 

 much less. 



Family 2. ASTACIDAE.* 



Crayfish. Body not so 

 large as in previous fam- 

 ily; rostrum without lat- 

 eral teeth: several genera 

 and over 100 species; in 

 fresh water. 



Key to the genera of 

 Astacidae here described : 

 «! Pacific slope craj^fish. 



1. ASTACUS 



02 Atlantic slope and 

 Mississippi valley 

 crayfish. 2. Cambarus 



crayfish showing 

 arraugement of internal organs (McMurrich) ; B, 

 diagram of cross section of the cephalothorax 

 showing gill chamber ; C, interior of gill chamber 

 of Astacus, the outer wall having been removed 

 (Siissw. F. Deut.). 1, pleurobranch ; 2, upper 

 arthobranch ; o, lower arthrobranch ; 4, podo- 

 branch ; 5, gill chamber ; 0, pleurobranch of the 

 last thoracic somite; 7, last periopod ; 8, gills; 

 y, first periopod ; 10, mouth ; 11, stomach ; 12, 

 liver ; 13, heart ; 14, gonad ; 15, dorsal artery ; 

 IG, intestine ; 17, anus ; 18, ventral artery ; 19, 

 nerve chord ; 20, kidney. 



1. Astacus Fabricius. 

 A pair of gills (pleuro- 

 branehs) on the last tho- 

 racic somite (Fig. 623, 

 C, 6), and 18 pairs in all: about 15 species, 5 on the Pacific slope, the 

 remainder in Europe and Asia. 



A. nigrescens Stimpson. Chelae naked on outer face; margins of 

 rostrum denticulate; length 10 cm.; color dark greenish: San Francisco 

 to Alaska, near the coast; used for food. 



2. Cambarusj Erichson. Common American crayfish (Fig. 623). 



* See "Monograph of the North American Astacidae," by H. A. Hagen, Mem. Mus. 

 Comp. Zool., Vol. 3, 1870. "The Crayfish," by T. H. Huxley, 1881. "A Revision of 

 the Astacidae," by W. Faxon, Mem. Mus. Comp. Zool., Vol. 10, 1885. "Observations 

 on the Astacidae," etc., by W. Faxon, Proc. U. S. Nat. Mus., Vol. 20, p. 643, 1898. 

 "Synopsis of the Astacidae of North America," by W. P. Hay, Am. Nat., Vol. 83, p. 

 957, 1899. "The Young of the Crayfish Astacus and Cambarus," by E. A. Andrews, 

 Smithsonian Contributions to Knowledge, Vol. 35, p. 1, 1907. 



t See "Ecological Catalogue of the Crayfishes Belonging to the Genus Cambarus," 

 by J. Arthur Harris, Kansas Univ. Sci. Bull., Vol. 2, p. 51, 1903. "The Crawfishes 

 of the State of l*ennsylvania," by A. E. Ortmann, Memoirs of the Carnegie Museum, 

 Vol. 2, p. 343, 1906. "Breeding Habits of the Crayfish," by E. A. Andrews, Am. Nat., 

 Vol. 38, p. 165, 1904. 



