opilio is 1.5 to 2.0 times the length of the preorbi- 

 tals (from our samples from Chukchi Sea); and on 

 C. opilio elongatus all three spines are nearly the 

 same length (Kurata 1963b); 4) C. bairdi has a 

 rudimentary spine immediately posterior to each 

 eye; in C. opilio and C. opilio elongatus this spine, 

 though still minute, is quite conspicuous. 



Key to Megalopa of Some Common 

 Brachyuran genera of the Northwest 



The following key is to provide a means of iden- 

 tification of some common Brachyura megalopa of 

 the northwest to the generic level. As only charac- 

 teristics which can be determined without dissec- 

 tion have been used, the key should be used for 

 preliminary sorting. The present state of knowl- 

 edge of these megalopa comes from six sources 

 (i.e., Hart 1960; Kurata 1963a, b; Poole 1966; 

 Makarov 1967; Motoh 1973). Key modified after 

 Makarov (1967). 



A. Carapace bears dorsal spines 



B. Posterior part of carapace bears one 



spine Hyas; Oregonia; Cancer 



B'. Posterior part of carapace bears two 



spines Chionoecetes 



A'. Carapace bears no dorsal spines 



B. Angles of posterior margin of abdom- 

 inal somite 5 reach beyond somite 6 



Telmessus 



B'. Angles of posterior margin of abdom- 

 inal somite 5 reach to middle of 

 somite 6 Erimacrus 



Acknowledgments 



Funding in partial support of this project was 

 made available through U.S. Department of 

 Commerce (NOAA) contract no. 03-5-022-56 to 

 H. M. Feder, Institute of Marine Science, Univer- 

 sity of Alaska, Fairbanks. 



The authors thank the following people: George 

 Mueller, Curator of Marine Collections, Univer- 

 sity of Alaska, gave guidance with the drawings; 

 H. M. Feder and Evan Haynes, National Marine 

 Fisheries Service, NOAA, reviewed the manu- 

 script; R. T. Cooney, Institute of Marine Science, 

 University of Alaska, Fairbanks, loaned the 

 Chionoecetes bairdi larvae collected 21 May 1973; 

 and Bruce Wing, National Marine Fisheries Ser- 

 vice, NOAA, supplied the Chionoecetes opilio 

 megalopa from the Chukchi Sea. 



Literature Cited 

 Garth, j. S. 



1958. Brachyura of the Pacific coast of America. 



Oxyrhyncha. Allan Hancock Pac. Exped. 21(2), 854 p. 

 HART, J. F. L. 



1960. The larval development of British Columbia 



Brachyura. II. Majidae, subfamily Oregoniinae. Can. J. 



Zool. 38:539-546. 



Haynes, E. 



1973. Descriptions of prezoeae and stage I zoeae of 

 Chionoecetes bairdi and C. opilio. (Oxyrhyncha, 

 Oregoniinae). Fish. Bull., U.S. 71:769-775. 

 KURATA, H. 



1963a. Larvae of Decapoda Crustacea of Hokkaido. 1. 

 Atelecyclidae (Atelecyclinae). [In Jap., Engl, 

 summ.] Bull. Hokkaido Reg. Rish. Res. Lab. 27:13-24. 



1963b. Larvae of Decapoda Crustacea of Hokkaido. 2. 

 Majidae (Pisinae). [In Jap., Engl, summ.] Bull. Hok- 

 kaido Reg. Fish. Res. Lab. 27:25-31. (Fish. Res. Board 

 Can., Transl. Ser. 1124.) 



Makarov, r. r. 



1967. Larvae of the shrimps and crabs of the West 

 Kamtschatkan Shelf and their distribution. Translated 

 from Russian by B. Haigh. Natl. Lending Libr. Sci. 

 Technol., Boston Spa, Engl., 199 p. 

 MOTOH, H. 



1973. Laboratory-reared zoeae and megalopae of zuwai 

 crab from the Sea of Japan. Bull. Jap. Soc. Sci. Fish. 

 39:1223-1230. 

 POOLE, R. L. 



1966. A description of laboratory-reared zoeae of Cancer 

 magister Dana, and megalopae taken under natural con- 

 ditions (Decapoda, Brachyura). Crustaceana 11:83-97. 



Stephen C. Jewett 



Institute of Marine Science 

 University of Alaska 

 Fairbanks, AK 99701 



RICHARD E. HAIGHT 



Northwest and Alaska Fisheries Center Auke Bay Laboratory 

 National Marine Fisheries Service, NOAA 

 P.O. Box 155, Auke Bay, AK 99821 



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