part 1 garth: pacific oxyrhyncha 149 



Type: The circum-boreal Cancer opilio O. Fabricius, 1788, type of 

 Chionoecetes Kroyer by monotypy. 



Description: Carapace broad, depressed, more or less tuberculated or 

 spinose. Rostrum short, flattened and notched, not depressed. Orbits 

 shallow, open above, the short, thick eye peduncles visible from above 

 when retracted. No preorbital spine; postorbital [spine] present. Basal 

 antennal [article] very narrow, with a terminal spine; second and third 

 [articles] not dilated; flagellum short. Ambulatory legs more or less 

 compressed and of moderate length. 



Abdomen seven- [segmented] [in both sexes]. (Holmes) 



Range: Eastern Pacific: from Bering Strait and the Aleutian Islands 

 to Cortez Bank, opposite the United States-Mexico boundary; Western 

 Pacific: from Kamchatka to off Kinkazan, Japan, and Oki Islands in 

 the Japan Sea. Siberian, Alaskan, and Canadian Arctic. Western 

 Atlantic: from west coast of Greenland to Casco Bay, Maine. Shallow 

 water to 1,625 fathoms. 



Key to the Species of Chionoecetes 



la. Carapace tuberculate, or with a few spinate tubercles, branchial 



regions depressed, not concealing lateral margins. Rostrum not 



sharply inclined. Meri of ambulatory legs broadened 



2a. Length and breadth of carapace subequal. Spines of ptery- 



gostomian row not increasing in size posteriorly. Seventh 



segment of male abdomen strongly inserted into sixth 



opilio 



2b. Carapace broader than long, lateral margins deeply scal- 

 loped. Last 3 or 4 spines of pterygostomian row large. 

 Seventh segment of male abdomen less strongly inserted 



into sixth than in 2a bairdi 



lb. Carapace spinulous, branchial regions expanded to conceal 

 lateral margins. Rostrum sharply inclined upward. Meri of 

 ambulatory legs slender 



3a. Interspace between branchial regions deep. Two small sub- 

 equal spines at curve made by intersection of the two dorsal 



branchial ridges tanneri 



3b. Interspace between branchial regions shallow. A large spine 

 at angle made by intersection of the two dorsal branchial 

 ridges angulatus 



